yabasic(1)yabasic(1)NAMEyabasic - yet another Basic
SYNOPSISyabasic [options] [filename [arguments]]
DESCRIPTION
Yabasic is a simple, old fashioned basic interpreter with some addi‐
tional features like subroutines and libraries. Grafics and printing
are limited but very easy to use.
Yabasic is documented within the file yabasic.htm, which may or may not
be present on your system; in any case this document can be found on
www.yabasic.de.
However, this html-document has been inserted as a preformatted text
into this man page. Note, that you will at least need an eighty-column
terminal to read this text without ugly wrapped lines.
Moreover, this man-page contains some chapters, that are specific for
windows and do not directly apply to your system.
Finally note, that this man-page (unlike the html-document it is based
upon) does not contain hyperlinks. In fact due to its large number of
hyperlinks the html-document is much easier to read, understand and
navigate than this man-page. However if you are determined to read this
man-page, there are three especially useful ways to navigate; each
works by searching for specific strings:
· To go to a specific chapter (e.g. Chapter 5, "All commands and
functions of yabasic"), you may look up the number of this chapter
in the table of contents and search for the string "Chapter 5.";
please note the uppercase "C" and the dot.
· To go to the description of a specific command (e.g. the for-com‐
mand), you may search for its name followed by a single space and a
double hyphen. In the example this would be "for --".
· The description of functions contain the name of the function fol‐
lowed by parens ("()"). Therefore, to find the description of the
sine-function, you should search for "sin\(\) --". Note, that you
will probably need to escape those parens by prepending them with a
backslash ("\").
But now for the documentation itself:
Yabasic
_________________________________________________________________
Table of Contents
1. Introduction
About this document
About yabasic
2. The yabasic-program under Windows
Starting yabasic
Options
The context Menu
3. The yabasic-program under Unix
Starting yabasic
Options
Setting defaults
4. Some features of yabasic, explained by topic
print, input and others
Control statements: loops, if and switch
Drawing and painting
Reading from and writing to files
Subroutines and Libraries
String processing
Arithmetic
Data and such
Other interesting commands.
5. All commands and functions of yabasic listed by topic
Number processing and conversion
Conditions and control structures
Data keeping and processing
String processing
File operations and printing
Subroutines and libraries
Other commands
Graphics and printing
6. All commands and functions of yabasic grouped alphabetically
A
B
C
D
E
F
G
H
I
L
M
N
O
P
R
S
T
U
V
W
X
Special characters
7. A grab-bag of some general concepts and terms
Logical shortcuts
Conditions and expressions
References on arrays
Specifying Filenames under Windows
Escape-sequences
Creating a standalone program from your yabasic-program
8. A few example programs
A very simple program
The demo of yabasic
9. The Copyright of yabasic
Chapter 1. Introduction
Table of Contents
About this document
About yabasic
About this document
This document describes yabasic. You will find information about the yabasic
interpreter (the program yabasic under Unix or yabasic.exe under Windows) as
well as the language (which is of course a sort of basic) itself.
This document applies to version 2.760 of yabasic
However, this document does not contain the latest news about yabasic or a
FAQ. As such information tends to change rapidly, it is presented online
only at www.yabasic.de.
Although basic has its reputation as a language for beginning programmers,
this is not an introduction to programming at large. Rather this text
assumes, that the reader has some (moderate) experience with writing and
starting computer programs.
About yabasic
yabasic is a traditional basic interpreter. It understands most of the
typical basic-constructs, like goto, gosub, line numbers, read, data or
string-variables with a trailing '$'. But on the other hand, yabasic
implements some more advanced programming-constructs like subroutines or
libraries (but not objects). yabasic works much the same under Unix and
Windows.
yabasic puts emphasis on giving results quickly and easily; therefore simple
commands are provided to open a graphic window, print the graphics or
control the console screen and get keyboard or mouse information. The
example below opens a window, draws a circle and prints the graphic:
open window 100,100
open printer
circle 50,50,40
text 10,50,"Press any key to get a printout"
clear screen
inkey$
close printer
close window
This example has fewer lines, than it would have in many other programming
languages. In the end however yabasic lacks behind more advanced and modern
programming languages like C++ or Java. But as far as it goes it tends to
give you results more quickly and easily.
Chapter 2. The yabasic-program under Windows
Table of Contents
Starting yabasic
Options
The context Menu
Starting yabasic
Once, yabasic has been set up correctly, there are three ways to start it:
1. Rightclick on your desktop: The desktop menu appears with a submenu
named new. From this submenu choose yabasic. This will create a new icon
on your desktop. If you rightclick on this icon, its context menu will
appear; choose Execute to execute the program.
2. As a variant of the way described above, you may simply create a file
with the ending .yab (e.g. with your favorite editor). Everything else
then works as described above.
3. From the start-menu: Choose yabasic from your start-menu. A
console-window will open and you will be asked to type in your program.
Once you are finished, you need to type return twice, and yabasic will
parse and execute your program.
Note
This is not the preferred way of starting yabasic ! Simply because the
program, that you have typed, can not be saved and will be lost
inevitably ! There is no such thing as a save-command and therefore no
way to conserve the program, that you have typed. This mode is only
intended for quick hacks, and short programs.
Options
Under Windows yabasic will mostly be invoked by double-clicking on an
appropriate icon; this way you do not have a chance to specify any of the
commandline options below. However, advanced users may add some of those
options to the appropriate entries in the registry.
All the options below may be abbreviated, as long as the abbreviation does
not become ambigous. For example, you may write -e instead of -execute.
-help or -?
Prints a short help message, which itself describes two further
help-options.
-version
Prints the version of yabasic.
-geometry +X-POSITION+Y-POSITION
Sets the position of the graphic window, that is opened by open
window (the size of this window, of course, is specified within the
open window-command). An example would be -geometry +20+10, which
would place the graphic window 10 pixels below the upper border and
20 pixels right of the left border of the screen. This value cannot
be changed, once yabasic has been started.
-font NAME-OF-FONT
Name of the font, which will be used for graphic-text; can be any of
decorative, dontcare, modern, roman, script, swiss. You may append a
fontsize (measured in pixels) to any of those fontnames; for example
-font swiss30 chooses a swiss-type font with a size of 30 pixels.
-bind NAME-OF-STANDALONE-PROGRAM
Create a standalone program (whose name is specified by
NAME-OF-STANDALONE-PROGRAM) from the yabasic-program, that is
specified on the commandline. See the section about creating a
standalone-program for details.
-execute A-PROGRAM-AS-A-SINGLE-STRING
With this option you may specify some yabasic-code to be executed
rigth away.This is useful for very short programs, which you do not
want to save within a file. If this option is given, yabasic will not
read any code from a file. Let's say, you have forgotten some of the
square numbers between 1 and 10; in this case the command yabasic-e
'for a=1 to 10:print a*a:next a' will give you the answer
immediately.
-infolevel INFOLEVEL
Change the infolevel of yabasic, where INFOLEVEL can be one of debug,
note, warning, error and fatal (the default is warning). This option
changes the amount of debugging-information yabasic produces.
However, normally only the author of yabasic (me !) would want to
change this.
-doc NAME-OF-A-PROGRAM
Print the embedded documentation of the named program. The embedded
documentation of a program consists of all the comments within the
program, which start with the special keyword doc. This documentation
can also be seen by choosing the corresponding entry from the
context-menu of any yabasic-program.
-librarypath DIRECTORY-WITH-LIBRARIES
Change the directory, wherein libraries will be searched and imported
(with the import-command). See also this entry for more information
about the way, libraries are searched.
The context Menu
Like every other icon under Windows, the icon of every yabasic-program has a
context menu offering the most frequent operations, that may be applied to a
yabasic-program.
Execute
This will invoke yabasic to execute your program. The same happens,
if you doubleclick on the icon.
Edit
notepad will be invoked, allowing you to edit your program.
View docu
This will present the embedded documentation of your program.
Embedded documentation is created with the special comment doc.
Chapter 3. The yabasic-program under Unix
Table of Contents
Starting yabasic
Options
Setting defaults
Starting yabasic
If your system administrator (vulgo root) has installed yabasic correctly,
there are three ways to start it:
1. You may use your favorite editor (emacs, vi ?) to put your program into
a file (e.g. foo). Make sure that the very first line starts with the
characters '#!' followed by the full pathname of yabasic (e.g.
'#!/usr/local/bin/yabasic'). This she-bang-line ensures, that your Unix
will invoke yabasic to execute your program (see also the entry for the
hash-character). Moreover, you will need to change the permissions of
your yabasic-program foo, e.g. chmod u+x foo. After that you may invoke
yabasic to invoke your program by simply typing foo (without even
mentioning yabasic). However, if your PATH-variable does not contain a
single dot ('.') you will have to type the full pathname of your
program: e.g. /home/ihm/foo (or at least ./foo).
2. Save your program into a file (e.g. foo) and type yabasic foo. This
assumes, that the directory, where yabasic resides, is contained within
your PATH-variable.
3. Finally your may simply type yabasic (maybe it will be necessary to
include its full pathname). This will make yabasic come up and you will
be asked to type in your program. Once you are finished, you need to
type return twice, and yabasic will parse and execute your program.
Note
This is not the preferred way of starting yabasic ! Simply because the
program, that you have typed, can not be saved and will be lost
inevitably ! There is no such thing as a save-command and therefore no
way to conserve the program, that you have typed. This mode is only
intended for quick hacks, and short programs, i.e. for using yabasic as
some sort of fancy desktop calculator.
Options
yabasic accepts a number of options on the commandline. All these options
below may be abbreviated, as long as the abbreviation does not become
ambigous. For example you may write -e instead of -execute.
-help or -?
Prints a short help message, which itself describes two further
help-options.
-version
Prints the version of yabasic.
-fg FOREGROUND-COLOR or -foreground FOREGROUND-COLOR
Define the foreground color for the graphics-window (that will be
opened with open window). The usual X11 colornames, like red, green,
... are accepted. This value cannot be changed, once yabasic has been
started.
-bg BACKGROUND-COLOR or -background BACKGROUND-COLOR
Define the background color for the graphics-window. The usual X11
colornames are accepted. This value cannot be changed, once yabasic
has been started.
-geometry +X-POSITION+Y-POSITION
Sets the position of the graphic window, that is opened by open
window (the size of this window, of course, is specified with the
open window-command). An example would be +20+10, which would place
the graphic window 10 pixels below the upper border and 20 pixels
right of the left border of the screen. Note, that the size of the
window may not be specified here (well it may, but it will be ignored
anyway). This value cannot be changed, once yabasic has been started.
-display BACKGROUND-COLOR
Specify the display, where the graphics window of yabasic should
appear. Normally, however this value will be already present within
the environment variable DISPLAY.
-font NAME-OF-FONT
Name of the font, which will be used for text within the graphics
window.
-execute A-PROGRAM-AS-A-SINGLE-STRING
With this option you may specify some yabasic-code to be executed
rigth away.This is useful for very short programs, which you do not
want to save to a file. If this option is given, yabasic will not
read any code from a file. E.g.
yabasic-e 'for a=1 to 10:print a*a:next a'
prints the square numbers from 1 to 10.
-bind NAME-OF-STANDALONE-PROGRAM
Create a standalone program (whose name is specified by
NAME-OF-STANDALONE-PROGRAM) from the yabasic-program, that is
specified on the commandline. See the section about creating a
standalone-program for details.
-infolevel INFOLEVEL
Change the infolevel of yabasic where INFOLEVEL can be one of debug,
note, warning, error and fatal (the default is warning). This option
changes the amount of debugging-information yabasic produces.
However, normally only the author of yabasic (me !) would want to
change this.
-doc NAME-OF-A-PROGRAM
Print the embedded documentation of the named program. The embedded
documentation of a program consists of all the comments within the
program, which start with the special keyword doc.
-librarypath DIRECTORY-WITH-LIBRARIES
Change the directory from which libraries will be imported (with the
import-command). See also this entry for more information about the
way, libraries will be searched.
Setting defaults
If you want to set some options once for all, you may put them into your
X-Windows resource file. This is usually the file .Xresources or some such
within your home directory (type man X for details).
Here is a sample section, which may appear within this file:
yabasic*foreground: blue
yabasic*background: gold
yabasic*geometry: +10+10
yabasic*font: 9x15
This will set the foreground color of the graphic-window to blue and the
background color to gold. The window will appear at position 10,10 and the
text font will be 9x15.
Chapter 4. Some features of yabasic, explained by topic
Table of Contents
print, input and others
Control statements: loops, if and switch
Drawing and painting
Reading from and writing to files
Subroutines and Libraries
String processing
Arithmetic
Data and such
Other interesting commands.
This chapter has sections for some of the major features of yabasic and
names a few commands related with each area. So, depending on your interest,
you find the most important commands of this area named; the other commands
from this area may then be discovered through the links in the see
also-section.
print, input and others
The print-command is used to put text on the text screen. Here, the term
text screen stands for your terminal (under Unix) or the console window
(under Windows).
At the bottom line, print simply outputs its argument to the text window.
However, once you have called clear screen you may use advanced features
like printing colors or copying areas of text with getscreen$ or putscreen.
You may ask the user for input with the input-command; use inkey$ to get
each key as soon as it is pressed.
Control statements: loops, if and switch
Of course, yabasic has the goto- and gosub-statements; you may go to a label
or a line number (which is just a special kind of label). goto, despite its
bad reputation ([goto considered harmful]), has still its good uses; however
in many cases you are probably better off with loops like repeat-until,
while-wend or do-loop; you may leave any of these loops with the
break-statement or start the next iteration immediately with continue.
Decisions can be made with the if-statement, which comes either in a short
and a long form. The short form has no then-keyword and extends up to the
end of the line. The long form extends up to the final endif and may use
some of the keywords then (which introduces the long form), else or elsif.
If you want to test the result of an expression against many different
values, you should probably use the switch-statement.
Drawing and painting
You need to call open window before you may draw anything with either line,
circle, rectangle or triangle; all of these statements may be decorated with
clear or fill. If you want to change the colour for drawing, use colour.
Note however, that there can only be a single window open at any given
moment in time.
Evyerything you have drawn can be send to your printer too, if you use the
open printer command.
To allow for some (very) limited version of animated graphics, yabasic
offers the commands getbit$ and putbit, which retrieve rectangular regions
from the graphics-window into a string or vice versa.
If you want to sense mouse-clicks, you may use the inkey$-function.
Reading from and writing to files
Before you may read or write a file, you need to open it; once you are done,
you should close it. Each open file is designated by a simple number, which
might be stored within a variable and must be supplied if you want to access
the file. This is simply done by putting a hash ('#') followd by the number
of the file after the keyword input (for reading from) or print (for writing
to a file) respectively.
If you need more control, you may consider reading and writing one byte at a
time, using the multi-purpose commands peek and poke.
Subroutines and Libraries
The best way to break any yabasic-program into smaller, more manageable
chunks are subroutines and libraries. They are yabasic's most advanced means
of structuring a program.
Subroutines are created with the command sub. they accept parameters and may
return a value. Subroutines can be called much like any builtin function of
yabasic; therefore they allow to extend the language itself.
Once you have created a set of related subroutines and you feel that they
could be useful in other programs too, you may collect them into a library.
Such a library is contained within a separate file and may be included in
any of your programs, using the keyword import.
String processing
yabasic has the usual functions to extract parts from a string: left$, mid$
and right$. Note, that all of them can be assigned to, i.e. they may change
part of a string.
If you want to split a string into tokens you should use the functions token
or split.
There is quite a bunch of other string-processing functions like upper$
(converting to upper case), instr (finding one string within the other),
chr$ (converting an ascii-code into a character), glob (testing a string
against a pattern) and more. Just follow the links.
Arithmetic
Yabasic handles numbers and arithmetic: You may calculate trigonometric
functions like sin or atan, or logarithms (with log). Bitwise operations,
like and or or are available as well min or max (calculate the minimum or
maximum of its argument) or mod or int (reminder of a division or integer
part or a number).
Data and such
You may store data within your program within data-statements; during
execution you will probably want to read it into arrays, which must have
been dimed before.
Other interesting commands.
* Yabasic programs may start other programs with the commands system and
system$.
* peek and poke allow to get and set internal information; either for the
operating system (i.e. Unix or Windows) or yabasic itself.
* The current time or date can be retrieved with (guess what !) time$ and
date$.
Chapter 5. All commands and functions of yabasic listed by topic
Table of Contents
Number processing and conversion
Conditions and control structures
Data keeping and processing
String processing
File operations and printing
Subroutines and libraries
Other commands
Graphics and printing
Number processing and conversion
abs()
returns the absolute value of its numeric argument
acos()
returns the arcus cosine of its numeric argument
and()
the bitwise arithmetic and
asin()
returns the arcus sine of its numeric argument
atan()
returns the arcus tangens of its numeric argument
bin$()
converts a number into a sequence of binary digits
cos()
return the cosine of its single argument
dec()
convert a base 2 or base 16 number into decimal form
eor()
compute the bitwise exclusive or of its two arguments
euler
another name for the constant 2.71828182864
exp()
compute the exponential function of its single argument
frac()
return the fractional part of its numeric argument
int()
return the integer part of its single numeric argument
log()
compute the natural logarithm
max()
return the larger of its two arguments
min()
return the smaller of its two arguments
mod()
compute the remainder of a division
or()
arithmetic or, used for bit-operations
pi
a constant with the value 3.14159
ran()
return a random number
sig()
return the sign of its argument
sin()
return the sine of its single argument
sqr()
compute the square of its argument
sqrt()
compute the square root of its argument
tan()
return the tangens of its argument
xor()
compute the exclusive or
** or ^
raise its first argument to the power of its second
Conditions and control structures
and
logical and, used in conditions
break
breaks out of a switch statement or a loop
case
mark the different cases within a switch-statement
continue
start the next iteration of a for-, do-, repeat- or while-loop
default
mark the default-branch within a switch-statement
do
start a (conditionless) do-loop
else
mark an alternative within an if-statement
elsif
starts an alternate condition within an if-statement
end
terminate your program
endif
ends an if-statement
false
a constant with the value of 0
fi
another name for endif
for
starts a for-loop
gosub
continue execution at another point within your program (and return
later)
goto
continue execution at another point within your program (and never
come back)
if
evaluate a condition and execute statements or not, depending on the
result
label
mark a specific location within your program for goto, gosub or
restore
loop
marks the end of an infinite loop
next
mark the end of a for loop
not
negate an expression; can be written as !
on gosub
jump to one of multiple gosub-targets
on goto
jump to one of many goto-targets
on interrupt
change reaction on keyboard interrupts
logical or
logical or, used in conditions
pause
pause, sleep, wait for the specified number of seconds
repeat
start a repeat-loop
return
return from a subroutine or a gosub
sleep
pause, sleep, wait for the specified number of seconds
switch
select one of many alternatives depending on a value
then
tell the long from the short form of the if-statement
true
a constant with the value of 1
until
end a repeat-loop
wait
pause, sleep, wait for the specified number of seconds
wend
end a while-loop
while
start a while-loop
:
separate commands from each other
Data keeping and processing
arraydim()
returns the dimension of the array, which is passed as an array
reference
arraysize()
returns the size of a dimension of an array
data
introduces a list of data-items
dim
create an array prior to its first use
read
read data from data-statements
redim
create an array prior to its first use. A synonym for dim
restore
reposition the data-pointer
String processing
asc()
accepts a string and returns the position of its first character
within the ascii charset
chr$()
accepts a number and returns the character at this position within
the ascii charset
glob()
check if a string matches a simple pattern
hex$()
convert a number into hexadecimal
instr()
searches its second argument within the first; returns its position
if found
left$()
return (or change) left end of a string
len()
return the length of a string
lower$()
convert a string to lower case
ltrim$()
trim spaces at the left end of a string
mid$()
return (or change) characters from within a string
right$()
return (or change) the right end of a string
split()
split a string into many strings
str$()
convert a number into a string
token()
split a string into multiple strings
trim$()
remove leading and trailing spaces from its argument
upper$()
convert a string to upper case
val()
converts a string to a number
File operations and printing
at()
can be used in the print-command to place the output at a specified
position
beep
ring the bell within your computer; a synonym for bell
bell
ring the bell within your computer (just as beep)
clear screen
erases the text window
close
close a file, which has been opened before
close printer
stops printing of graphics
print color
print with color
print colour
see print color
eof
check, if an open file contains data
getscreen$()
returns a string representing a rectangular section of the text
terminal
inkey$
wait, until a key is pressed
input
read input from the user (or from a file) and assign it to a variable
line input
read in a whole line of text and assign it to a variable
open
open a file
open printer
open printer for printing graphics
print
Write to terminal or file
putscreen
draw a rectangle of characters into the text terminal
reverse
print reverse (background and foreground colors exchanged)
screen
as clear screen clears the text window
seek()
change the position within an open file
tell
get the current position within an open file
using
Specify the format for printing a number
#
either a comment or a marker for a file-number
@
synonymous to at
;
suppress the implicit newline after a print-statement
Subroutines and libraries
end sub
ends a subroutine definition
export
mark a function as globally visible
import
import a library
local
mark a variable as local to a subroutine
numparams
return the number of parameters, that have been passed to a
subroutine
return
return from a subroutine or a gosub
static
preserves the value of a variable between calls to a subroutine
step
specifies the increment step in a for-loop
sub
declare a user defined subroutine
Other commands
bind()
Binds a yabasic-program and the yabasic-interpreter together into a
standalone program.
compile
compile a string with yabasic-code on the fly
date$
returns a string with various components of the current date
doc
special comment, which might be retrieved by the program itself
docu$
special array, containing the contents of all docu-statement within
the program
error
raise an error and terminate your program
execute$()
execute a user defined subroutine, which must return a string
execute()
execute a user defined subroutine, which must return a number
exit
terminate your program
pause
pause, sleep, wait for the specified number of seconds
peek
retrieve various internal informations
peek$
retrieve various internal string-informations
poke
change selected internals of yabasic
rem
start a comment
sleep
pause, sleep, wait for the specified number of seconds
system$()
hand a statement over to your operating system and return its output
system()
hand a statement over to your operating system and return its
exitcode
time$
return a string containing the current time
to
this keyword appears as part of other statements
wait
pause, sleep, wait for the specified number of seconds
//
starts a comment
:
separate commands from each other
Graphics and printing
backcolor
specify the colour for subsequent drawing of the background
box
draw a rectancle. A synonym for rectangle
circle
draws a circle in the graphic-window
clear
Erase circles, rectangles or triangless
clear window
clear the graphic window and begin a new page, if prining is under
way
close curve
close a curve, that has been drawn by the line-command
close window
close the graphics-window
colour
specify the colour for subsequent drawing
dot
draw a dot in the graphic-window
fill
draw a filled circles, rectangles or triangles
getbit$()
return a string representing the bit pattern of a rectangle within
the graphic window
line
draw a line
mouseb
extract the state of the mousebuttons from a string returned by
inkey$
mousemod
return the state of the modifier keys during a mouseclick
mousex
return the x-position of a mouseclick
mousey
return the y-position of a mouseclick
new curve
start a new curve, that will be drawn with the line-command
open window
open a graphic window
putbit
draw a rectangle of pixels into the graphic window
rectangle
draw a rectangle
triangle
draw a triangle
text
write text into your graphic-window
window origin
move the origin of a window
Chapter 6. All commands and functions of yabasic grouped alphabetically
Table of Contents
A
B
C
D
E
F
G
H
I
L
M
N
O
P
R
S
T
U
V
W
X
Special characters
A
Table of Contents
abs() - returns the absolute value of its numeric argument
acos() - returns the arcus cosine of its numeric argument
and - logical and, used in conditions
and() - the bitwise arithmetic and
arraydim() - returns the dimension of the array, which is passed as an array
reference
arraysize() - returns the size of a dimension of an array
asc() - accepts a string and returns the position of its first character
within the ascii charset
asin() - returns the arcus sine of its numeric argument
at() - can be used in the print-command to place the output at a specified
position
atan() - returns the arcus tangens of its numeric argument
abs()
Name
abs() - returns the absolute value of its numeric argument
Synopsis
y=abs(x)
Description
If the argument of the abs-function is positive (e.g. 2) it is returned
unchanged, if the argument is negative (e.g. -1) it is returned as a
positive value (e.g. 1).
Example
print abs(-2),abs(2)
This example will print 2 2
See also
sig
acos()
Name
acos() - returns the arcus cosine of its numeric argument
Synopsis
x=acos(angle)
Description
The acos is the arcus cosine-function, i.e. the inverse of the cos-function.
Or, more elaborate: It Returns the angle (in radian, not degree !), which,
fed to the cosine-function will produce the argument passed to the
acos-function.
Example
print acos(0.5),acos(cos(pi))
This example will print 1.0472 3.14159 which are pi/3 and pi respectively.
See also
cos, asin
and
Name
and - logical and, used in conditions
Synopsis
if (a and b) ...
while (a and b) ...
Description
Used in conditions (e.g within if, while or until) to join two expressions.
Returns true, if and only if its left and right argument are both true and
false otherwise.
Note, that logical shortcutsmay take place.
Example
input "Please enter a number" a
if (a>=1 and a<=9) print "your input is between 1 and 9"
See also
or,not
and()
Name
and() - the bitwise arithmetic and
Synopsis
x=and(a,b)
Description
Used to compute the bitwise and of both its argument. Both arguments are
treated as binary numbers (i.e. a series of 0 and 1); a bit of the resulting
value will then be 1, if both arguments have a 1 at this position in their
binary representation.
Note, that both arguments are silently converted to integer values and that
negative numbers have their own binary representation and may lead to
unexpected results when passed to and.
Example
print and(6,3)
This will print 2. This result is clear, if you note, that the binary
representation of 6 and 3 are 110 and 011 respectively; this will yield 010
in binary representaion or 2 as decimal.
See also
or, eor and not
arraydim()
Name
arraydim() - returns the dimension of the array, which is passed as an array
reference
Synopsis
a=arraydim(b())
Description
If you apply the arraydim()-function on a one-dimensional array (i.e. a
vector) it will return 1, on a two-dimensional array (i.e. a matrix) it will
return 2, and so on.
This is mostly used within subroutines, which expect an array among their
parameters. Such subroutines tend to use the arraydim-funtion to check, if
the array which has been passed, has the right dimension. E.g. a subroutine
to multiply two matrices may want to check, if it really is invoked with two
2-dimensional arrays.
Example
dim a(10,10),b(10)
print arraydim(a()),arraydim(b())
This will print 2 1, which are the dimension of the arrays a() and b(). You
may check out the function arraysize for a full-fledged example.
See also
arraysize and dim.
arraysize()
Name
arraysize() - returns the size of a dimension of an array
Synopsis
x=arraysize(a(),b)
Description
The arraysize-function computes the size of a specified dimension of a
specified array. Here, size stands for the maximum number, that may be used
as an index for this array. The first argument to this function must be an
reference to an array, the second one specifies, which of the multiple
dimensions of the array should be taken to calculate the size.
An Example involving subroutines: Let's say, an array has been declared as
dim a(10,20) (that is a two-dimensional array or a matrix). If this array is
passed as an array reference to a subroutine, this sub will not know, what
sort of array has been passed. With the arraydim-function the sub will be
able to find the dimension of the array, with the arraysize-function it will
be able to find out the size of this array in its two dimensions, which will
be 10 and 20 respectively.
Our sample array is two dimensional; if you envision it as a matrix this
matrix has 10 lines and 20 columns (see the dim-statement above. To state it
more formally: The first dimension (lines) has a size of 10, the second
dimension (columns) has a size of 20; these mumbers are those returned by
arraysize(a(),1) and arraysize(a(),2) respectively. Refer to the example
below for a typical usage.
Example
rem
rem This program adds two matrices elementwise.
rem
dim a(10,20),b(10,20),c(10,20)
rem initialization of the arrays a() and b()
for y=1 to 10:for x=1 to 20
a(y,x)=int(ran(4)):b(y,x)=int(ran(4))
next x:next y
matadd(a(),b(),c())
print "Result:"
for x=1 to 20
for y=10 to 1 step -1
print c(y,x)," ";
next y
print
next x
sub matadd(m1(),m2(),r())
rem This sub will add the matrices m1() and m2()
rem elementwise and store the result within r()
rem This is not very useful but easy to implement.
rem However, this sub excels in checking its arguments
rem with arraydim() and arraysize()
local x:local y
if (arraydim(m1())<>2 or arraydim(m2())<>2 or arraydim(r())<>2) then
error "Need two dimensional arrays as input"
endif
y=arraysize(m1(),1):x=arraysize(m1(),2)
if (arraysize(m2(),1)<>y or arraysize(m2(),2)<>x) then
error "The two matrices cannot be added elementwise"
endif
if (arraysize(r(),1)<>y or arraysize(r(),2)<>x) then
error "The result cannot be stored in the third argument"
endif
local xx:local yy
for xx=1 to x
for yy=1 to y
r(yy,xx)=m1(yy,xx)+m2(yy,xx)
next yy
next xx
end sub
See also
arraydim and dim.
asc()
Name
asc() - accepts a string and returns the position of its first character
within the ascii charset
Synopsis
a=asc(char$)
Description
The asc-function accepts a string, takes its first character and looks it up
within the ascii-charset; this position will be returned. The asc-function
is the opposite of the chr$-function. There are valid uses for asc, however,
comparing strings (i.e. to bring them into alphabetical sequence) is not
among them; in such many cases you might consider to compare strings
directly with <, = and > (rather than converting a string to a number and
comparing this number).
Example
input "Please enter a letter between 'a' and 'y': " a$
if (a$<"a" or a$>"y") print a$," is not in the proper range":end
print "The letter after ",a$," is ",chr$(asc(a$)+1)
See also
chr$
asin()
Name
asin() - returns the arcus sine of its numeric argument
Synopsis
angle=asin(x)
Description
The acos is the arcus sine-function, i.e. the inverse of the sin-function.
Or, more elaborate: It Returns the angle (in radian, not degree !), which,
fed to the sine-function will produce the argument passed to the
asin-function.
Example
print asin(0.5),asin(sin(pi))
This will print 0.523599 -2.06823e-13 which is pi and almost 0 respectively.
See also
sin, acos
at()
Name
at() - can be used in the print-command to place the output at a specified
position
Synopsis
clear screen
print at(a,b)
print @(a,b)
Description
The at-clause takes two numeric arguments (e.g. at(2,3)) and can be inserted
after the print-keyword. at() can be used only if clear screen has been
executed at least once within the program (otherwise you will get an error).
The two numeric arguments of the at-function may range from 0 to the width
of your terminal minus 1, and from 0 to the height of your terminal minus 1;
if any argument exceeds these values, it will be truncated accordingly.
However, yabasic has no influence on the size of your terminal (80x25 is a
common, but not mandatory), the size of your terminal and the maximum values
acceptable within the at-clause may vary. To get the size of your terminal
you may use the peek-function: peek("screenwidth") returns the width of your
terminal and peek("screenheight") its height.
Example
clear screen
maxx=peek("screenwidth")-1:maxy=peek("screenheight")-1
for x=0 to maxx
print at(x,maxy*(0.5+sin(2*pi*x/maxx)/2)) "*"
next x
This example plots a full period of the sine-function across the screen.
See also
print, clear screen, color
atan()
Name
atan() - returns the arcus tangens of its numeric argument
Synopsis
angle=atan(a,b)
angle=atan(a)
Description
The atan is the arcus-tangens-function, i.e. the inverse of the
tan-function. Or, more elaborate: It Returns the angle (in radian, not
degree !), which, fed to the tan-function will produce the argument passed
to the atan-function.
The atan-function has a second form, which accepts two arguments: atan(a,b)
which is (mostly) equivilantly to atan(a/b) except for the fact, that the
two-argument-form returns an angle in the range -pi to pi, whereas the
one-argument-form returns an angle in the range -pi/2 to pi/2. To understand
this you have to be good at math.
Example
print atan(1),atan(tan(pi)),atan(-0,-1),atan(-0,1)
This will print 0.463648 2.06823e-13 -3.14159 3.14159 which is pi/4, almost
0, -pi and pi respectively.
See also
tan, sin
B
Table of Contents
backcolor - change color for background of graphic window
backcolour - see backcolor
beep - ring the bell within your computer; a synonym for bell
bell - ring the bell within your computer (just as beep)
bin$() - converts a number into a sequence of binary digits
bind() - Binds a yabasic-program and the yabasic-interpreter together into a
standalone program.
box - draw a rectancle. A synonym for rectangle
break - breaks out of a switch statement or a loop
backcolor
Name
color - change color for background of graphic window
Synopsis
backcolour red,green,blue
backcolour "red,green,blue"
Description
Change the color, that becomes visible, if any portion of the window is
erased, e.g. after clear window or clear line. Note however, that parts of
the window, that display the old background color will not change.
As with the color-command, the new background color can either be specified
as a triple of three numbers or as a single string, that contains those
three numbers sperated by commas.
Example
open window 255,255
for x=10 to 235 step 10:for y=10 to 235 step 10
backcolour x,y,0
clear window
sleep 1
next y:next x
This changes the background colour of the graphic window repeatidly and
clears it every time, so that it is filled with the new background colour.
See also
open window, color, line, rectangle, triangle, circle
backcolour
Name
backcolour - see backcolor
Synopsis
backcolour red,green,blue
backcolour "red,green,blue"
See also
color
beep
Name
beep - ring the bell within your computer; a synonym for bell
Synopsis
beep
Description
The bell-command rings the bell within your computer once. This command is
not a sound-interface, so you can neither vary the length or the height of
the sound (technically, it just prints \a). bell is exactly the same as
beep.
Example
beep:print "This is a problem ..."
See also
beep
bell
Name
bell - ring the bell within your computer (just as beep)
Synopsis
bell
Description
The beep-command rings the bell within your computer once. beep is a synonym
for bell.
Example
print "This is a problem ...":beep
See also
bell
bin$()
Name
bin$() - converts a number into a sequence of binary digits
Synopsis
hexadecimal$=bin$(decimal)
Description
The bin$-function takes a single numeric argument an converts it into a
string of binary digits (i.e. zeroes and ones). If you pass a negative
number to bin$, the resulting string will be preceeded by a '-'.
If you want to convert the other way around (i.e. from binary to decimal)
you may use the dec-function.
Example
for a=1 to 100
print bin$(a)
next a
This example prints the binary representation of all digits between 1 and
100.
See also
hex$, dec
bind()
Name
bind() - Binds a yabasic-program and the yabasic-interpreter together into a
standalone program.
Synopsis
bind("foo.exe")
Description
The bind-command combines your own yabasic-program (plus all the libraries
it does import) and the interpreter by copying them into a new file, whose
name is passed as an argument. This new program may then be executed on any
computer, even if it does not have yabasic installed.
Please see the section about creating a standalone-program for details.
Example
if (!peek("isbound")) then
bind "foo"
print "Successfully created the standalone executable 'foo' !"
exit
endif
print "Hello World !"
This example creates a standalone program foo from itself.
See also
The section about creating a standalone-program, the peek-function and the
commandline options for Unix and Windows.
box
Name
box - draw a rectancle. A synonym for rectangle
Synopsis
See the rectangle-command.
Description
The box-command does exactly the same as the rectangle-command; it is just a
synonym. Therefore you should refer to the entry for the rectangle-command
for further information.
break
Name
break - breaks out of a switch statement or a loop
Synopsis
break
Description
break transfers control immediately outside the enclosing loop or switch
statement. This is the preferred way of leaving a such a statement (rather
than goto, which is still possible in most cases).
Example
for a=1 to 10
break
print "Hi"
next a
while(1)
break
print "Hi"
wend
repeat
break
print "Hi"
until(0)
switch 1
case 1:break
case 2:case 3:print "Hi"
end switch
This example prints nothing at all, because each of the loops (and the
switch-statement) does an immediate break (before it could print any "Hi").
See also
for, while, repeat and switch.
C
Table of Contents
case - mark the different cases within a switch-statement
chr$() - accepts a number and returns the character at this position within
the ascii charset
circle - draws a circle in the graphic-window
clear - Erase circles, rectangles or triangles
clear screen - erases the text window
clear window - clear the graphic window and begin a new page, if prining is
under way
close - close a file, which has been opened before
close curve - close a curve, that has been drawn by the line-command
close printer - stops printing of graphics
close window - close the graphics-window
color - change color for any subsequent drawing-command
colour - see color
compile - compile a string with yabasic-code on the fly
continue - start the next iteration of a for-, do-, repeat- or while-loop
cos() - return the cosine of its single argument
case
Name
case - mark the different cases within a switch-statement
Synopsis
switch a
case 1
case 2
...
end switch
switch a$
case "a"
case "b"
...
end switch
Description
Please see the switch-statement.
Example
input a
switch(a)
case 1:print "one":break
case 2:print "two":break
default:print "more"
end switch
Depending on your input (a number is expected) this code will print one or
two or otherwise more.
See also
switch
chr$()
Name
chr$() - accepts a number and returns the character at this position within
the ascii charset
Synopsis
character$=chr$(ascii)
Description
The chr$-function is the opposite of the asc-function. It looks up and
returns the character at the given position within the ascii-charset. It's
typical use is to construct nonprintable characters which do not occur on
your keyboard.
Nevertheless you won't use chr$ as often as you might think, because the
most important nonprintable characters can be constructed using
escape-sequences using the \-character (e.g. you might use \n instead of
chr$(10) wherever you want to use the newline-character).
Example
print "a",chr$(10),"b"
This will print the letters 'a' and 'b' in different lines because of the
intervening newline-character, which is returned by chr$(10).
See also
asc
circle
Name
circle - draws a circle in the graphic-window
Synopsis
circle x,y,r
clear circle x,y,r
fill circle x,y,r
clear fill circle x,y,r
Description
The circle-command accepts three parameters: The x- and y-coordinates of the
center and the radius of the circle.
Some more observations related with the circle-command:
* The graphic-window must have been opened already.
* The circle may well extend over the boundaries of the window.
* If you have issued open printer before, the circle will finally appear
in the printed hardcopy of the window.
* fill circle will draw a filled (with black ink) circle.
* clear circle will erase (or clear) the outline of the circle.
* clear fill circle or fill clear circle will erase the full area of the
circle.
Example
open window 200,200
for n=1 to 2000
x=ran(200)
y=ran(200)
fill circle x,y,10
clear fill circle x,y,8
next n
This code will open a window and draw 2000 overlapping circles within. Each
circle is drawn in two steps: First it is filled with black ink (fill circle
x,y,10), then most of this circle is erased again (clear fill circle x,y,8).
As a result each circle is drawn with an opaque white interior and a 2-pixel
outline (2-pixel, because the radii differ by two).
See also
open window, open printer, line, rectangle, triangle
clear
Name
clear - Erase circles, rectangles or triangles
Synopsis
clear rectangle 10,10,90,90
clear fill circle 50,50,20
clear triangle 10,10,20,20,50,30
Description
May be used within the circle, rectangle or triangle command and causes
these shapes to be erased (i.e. be drawn in the colour of the background).
fill can be used in conjunction with and whereever the fill-clause may
appear. Used alone, clear will erase the outline (not the interior) of the
shape (circle, rectangle or triangle); together with fill the whole shape
(including its interior) is erased.
Example
open window 200,200
fill circle 100,100,50
clear fill rectangle 10,10,90,90
This opens a window and draws a pacman-like figure.
See also
clear, circle, rectangle, triangle
clear screen
Name
clear screen - erases the text window
Synopsis
clear screen
Description
clear screen erases the text window (the window where the output of print
appears).
It must be issued at least once, before some advanced screen-commands (e.g.
print at or inkey$) may be called; this requirement is due to some
limititations of the curses-library, which is used by yabasic under Unix for
some commands.
Example
clear screen
print "Please press a key : ";
a$=inkey$
print a$
The clear screen command is essential here; if it would be omitted, yabasic
would issue an error ("need to call 'clear screen' first") while trying to
execute the inkey$-function.
See also
inkey$
clear window
Name
clear window - clear the graphic window and begin a new page, if prining is
under way
Synopsis
clear window
Description
clear window clears the graphic window. If you have started prining the
graphic via open printer, the clear window-command starts a new page as
well.
Example
open window 200,200
open printer "t.ps"
for a=1 to 10
if (a>1) clear window
text 100,100,"Hallo "+str$(a)
next a
close printer
close window
This example prints 10 pages, with the text "Hello 1", "Hello 2", ... and so
on. The clear screen-command clears the graphics window and starts a new
page.
See also
open window, open printer
close
Name
close - close a file, which has been opened before
Synopsis
close filenum
close # filenum
Description
The close-command closes an open file. You should issue this command as soon
as you are done with reading from or writing to a file.
Example
open "my.data" for reading as 1
input #1 a
print a
close 1
This program opens the file "my.data", reads a number from it, prints this
number and closes the file again.
See also
open
close curve
Name
close curve - close a curve, that has been drawn by the line-command
Synopsis
new curve
line to x1,y1
close curve
Description
The close curve-command closes a sequence of lines, that has been drawn by
repeated line to-commands.
Example
open window 200,200
new curve
line to 100,50
line to 150,150
line to 50,150
close curve
This example draws a triangle: The three line to-commands draw two lines;
the final line is however not drawn explicitly, but drawn by the close
curve-command.
See also
line, new curve
close printer
Name
close printer - stops printing of graphics
Synopsis
close printer
Description
The close printer-command ends the printing graphics. Between open printer
and close printer everything you draw (e.g. circles, lines ...) is sent to
your printer. close printer puts an end to printing and will make your
printer eject the page.
Example
open window 200,200
open printer
circle 100,100,50
close printer
close window
As soon as close printer is executed, your printer will eject a page with a
circle on it.
See also
open printer
close window
Name
close window - close the graphics-window
Synopsis
close window
Description
The close window-command closes the graphics-window, i.e. it makes it
disappear from your screen. It includes an implicit close printer, if a
printer has been opened previously.
Example
open window 200,200
circle 100,100,50
close window
This example will open a window, draw a circle and close the window again;
all this without any pause or delay, so the window will be closed before you
may regard the circle..
See also
open window
color
Name
color - change color for any subsequent drawing-command
Synopsis
colour red,green,blue
colour "red,green,blue"
Description
Change the color, in which lines, dots, circles, rectangles or triangles are
drawn. The color-command accepts three numbers in the range 0 ... 255 (as in
the first line of the synopsis above). Those numbers specify the intensity
for the primary colors red, green and blue respectively. As an example
255,0,0 is red and 255,255,0 is yellow.
Alternatively you may specify the color with a single string (as in the
second line of the synopsis above); this string should contain three
numbers, seperated by commas. As an example "255,0,255" would be violet.
Using this variant of the colour-command, you may use symbolic names for
colours:
open window 100,100
yellow$="255,255,0"
color yellow$
text 50,50,"Hallo"
, which reads much clearer.
Example
open window 255,255
for x=10 to 235 step 10:for y=10 to 235 step 10
colour x,y,0
fill rectangle x,y,x+10,y+10
next y:next x
This fills the window with coloured rectangles. However, none of the used
colours contains any shade of blue, because the color-command has always 0
as a third argument.
See also
open window, backcolor, line, rectangle, triangle, circle
colour
Name
colour - see color
Synopsis
colour red,green,blue
colour "red,green,blue"
See also
color
compile
Name
compile - compile a string with yabasic-code on the fly
Synopsis
compile(code$)
Description
This is an advanced command (closely related with the execute-command). It
allows you to compile a string of yabasic-code (which is the only argument).
Afterwards the compiled code is a normal part of your program.
Note, that there is no way to remove the compiled code.
Example
compile("sub mysub(a):print a:end sub")
mysub(2)
This example creates a function named mysub, which simply prints its single
argument.
See also
execute
continue
Name
continue - start the next iteration of a for-, do-, repeat- or while-loop
Synopsis
continue
Description
You may use continue within any loop to start the next iteration
immediately. Depending on the type of the loop, the loop-condition will or
will not be checked. Especially: for- and while-loops will evaluate their
respective conditions, do- and repeat-loops will not.
Remark: Another way to change the flow of execution within a loop, is the
break-command.
Example
for a=1 to 100
if mod(a,2)=0 continue
print a
next a
This example will print all odd numbers between 1 and 100.
See also
for, do, repeat, while, break
cos()
Name
cos() - return the cosine of its single argument
Synopsis
x=cos(angle)
Description
The cos-function expects an angle (in radian) and returns its cosine.
Example
print cos(pi)
This example will print -1.
See also
acos, sin
D
Table of Contents
data - introduces a list of data-items
date$ - returns a string with various components of the current date
dec() - convert a base 2 or base 16 number into decimal form
default - mark the default-branch within a switch-statement
dim - create an array prior to its first use
do - start a (conditionless) do-loop
doc - special comment, which might be retrieved by the program itself
docu$ - special array, containing the contents of all docu-statement within
the program
dot - draw a dot in the graphic-window
data
Name
data - introduces a list of data-items
Synopsis
data 9,"world"
read b,a$
Description
The data-keyword introduces a list of comma-seperated list of strings or
numbers, which may be retrieved with the read-command.
The data-command itself does nothing; it just stores data. A single
data-command may precede an arbitrarily long list of values, in which
strings or numbers may be mixed at will.
yabasic internally uses a data-pointer to keep track of the current location
within the data-list; this pointer may be reset with the restore-command.
Example
do
restore
for a=1 to 4
read num$,num
print num$,"=",num
next a
loop
data "eleven",11,"twelve",12,"thirteen",13,"fourteen",14
This example just prints a series of lines eleven=11 up to fourteen=14 and
so on without end.
The restore-command ensures that the list of data-items is read from the
start with every iteration.
See also
read, restore
date$
Name
date$ - returns a string with various components of the current date
Synopsis
a$=date$
Description
The date$-function (which must be called without parantheses; i.e. date$()
would be an error) returns a string containing various components of a date;
an example would be 4-05-27-2004-Thu-May. This string consists of various
fields seperated by hyphens ("-"):
* The day within the week as a number in the range 0 (=sunday) to 6
(=saturday) (in the example above: 4, i.e. thursday).
* The month as a number in the range 1 (=january) to 12 (=december) (in
the example: 5 which stands for may).
* The day within the month as a number in the range 1 to 31 (in the
example: 27).
* The full, 4-digit year (in the example: 2004, which reminds me that I
should adjust the clock within my computer ...).
* The abbreviated name of the day within the week (Mon to Sun).
* The abbreviated name of the month (Jan to Dec).
Therefore the whole example above (4-05-27-2004-Thu-May) would read: day 4
in the week (counting from 0), May 27 in the year 2004, which is a thursday
in May.
Note, that all fields within the string returned by date$ have a fixed with
(numbers are padded with zeroes); therefore it is easy to extract the
various fields of a date format with mid$.
Example
rem Two ways to print the same ...
print mid$(date$,3,10)
dim fields$(6)
a=split(date$,fields$(),"-")
print fields$(2),"-",fields$(3),"-",fields$(4)
This example shows two different techniques to extract components from the
value returned by date$. The mid$-function is the preferred way, but you
could just as well split the return-value of date$ at every "-" and store
the result within an array of strings.
See also
time$
dec()
Name
dec() - convert a base 2 or base 16 number into decimal form
Synopsis
a=dec(number$)
a=dec(number$,base)
Description
The dec-function takes the string-representation of a base-2 or base-16
(which is the default) number and converts it into a decimal number. The
optional second argument (base) might be used to specify a base other than
16. However, currently only base 2 or base 16 are supported.
Example
input "Please enter a binary number: " a$
print a$," is ",dec(a$)
See also
bin$, hex$
default
Name
default - mark the default-branch within a switch-statement
Synopsis
switch a+3
case 1
...
case 2
...
default
...
end switch
Description
The default-clause is an optional part of the switch-statement (see there
for more information). It introduces a series of statements, that should be
executed, if none of the casese matches, that have been specified before
(each with its own case-clause).
So default specifies a default to be executed, if none of the explicitly
named cases matches; hence its name.
Example
print "Please enter a number between 0 and 6,"
print "specifying a day in the week."
input d
switch d
case 0:print "Monday":break
case 1:print "Tuesday":break
case 2:print "Wednesday":break
case 3:print "Thursday":break
case 4:print "Friday":break
case 5:print "Saturday":break
case 6:print "Sunday":break
default:print "Hey you entered something invalid !"
end switch
This program translates a number between 0 and 6 into the name of a weekday;
the default-case is used to detect (and complain about) invalid input.
See also
sub, case
dim
Name
dim - create an array prior to its first use
Synopsis
dim array(x,y)
dim array$(x,y)
Description
The dim-command prepares one or more arrays (of either strings or numbers)
for later use. This command can also be used to enlarges an existing array.
When an array is created with the dim-statement, memory is allocated and all
elements are initialized with either 0 (for numerical arrays) or "" (for
string arrays).
If the array already existed, and the dim-statement specifies a larger size
than the current size, the array is enlarged and any old content is
preserved.
Note, that dim cannot be used to shrink an array: If you specify a size,
that is smaller than the current size, the dim-command does nothing.
Finally: To create an array, that is only known within a single subroutine,
you should use the command local, which creates local variables as well as
local arrays.
Example
dim a(5,5)
for x=1 to 5:for y=1 to 5
a(x,y)=int(ran(100))
next y:next x
printmatrix(a())
dim a(7,7)
printmatrix(a())
sub printmatrix(ar())
local x,y,p,q
x=arraysize(ar(),1)
y=arraysize(ar(),2)
for q=1 to y
for p=1 to y
print ar(p,q),"\t";
next p
print
next q
end sub
This example creates a 2-dimenional array (i.e. a matrix) with the
dim-statement and fills it with random numbers. The second dim-statement
enlarges the array, all new elements are filled with 0.
The subroutine printmatrix just does, what its name says.
See also
arraysize, arraydim, local
do
Name
do - start a (conditionless) do-loop
Synopsis
do
loop
Description
Starts a loop, which is terminated by loop; everything between do and loop
will be repeated forever. This loop has no condition, so it is an infinite
loop; note however, that a break- or goto-statement might be used to leave
this loop anytime.
Example
do
a=a+1
print a
if (a>100) break
loop
This example prints the numbers between 1 and 101. The break-statement is
used to leave the loop.
See also
loop, repeat, while, break
doc
Name
doc - special comment, which might be retrieved by the program itself
Synopsis
doc This is a comment
docu This is another comment
Description
Introduces a comment, which spans up to the end of the line. But other than
the rem-comment, any docu-comment is collected within the special
docu$-array and might be retrieved later on. Moreover you might invoke
yabasic-docu foo.yab on the commandline to retrieve the embedded
documentation within the program foo.yab.
Instead of doc you may just as well write docu or even documentation.
Example
rem Hi, this has been written by me
rem
doc This program asks for a number and
doc prints this number multiplied with 2
rem
rem Print out rhe above message
for a=1 to arraysize(docu$()):print docu$(a):next a
rem Read and print the number
input "Please input a number: " x
print x*2
This program uses the comments within its code to print out a help message
for the user.
The contents of the doc-lines are retrieved from the docu$-array; if you do
not want a comment to be collected within this array, use the rem-statement
instead.
See also
docu$, rem
docu$
Name
docu$ - special array, containing the contents of all docu-statement within
the program
Synopsis
a$=docu$(1)
Description
Before your program is executed, yabasic collects the content of all the
doc-statements within your program within this 1-dimensional array (well
only those within the main-program, libraries are skipped).
You may use the arraysize function to find out, how many lines it contains.
Example
docu
docu This program reads two numbers
docu and adds them.
docu
rem retrieve and print the embedded documentation
for a=1 to arraysize(docu$(),1)
print docu$(a)
next a
input "First number: " b
input "Second number: " c
print "The sum of ",b," and ",c," is ",b+c
This program uses the embedded documentation to issue a usage-message.
See also
arraydim, rem
dot
Name
dot - draw a dot in the graphic-window
Synopsis
dot x,y
clear dot x,y
Description
Draws a dot at the specified coordinates within your graphic-window. If
printing is in effect, the dot appears on your printout too.
Use the functions peek("winheight") or peek("winwidth") to get the size of
your window and hence the boundaries of the coordinates specified for the
dot-command.
Example
open window 200,200
circle 100,100,100
do
x=ran(200):y=ran(200)
dot x,y
total=total+1
if (sqrt((x-100)^2+(y-100)^2)<100) in=in+1
print 4*in/total
loop
This program uses a well known algorithm to compute pi.
See also
line, open window
E
Table of Contents
else - mark an alternative within an if-statement
elsif - starts an alternate condition within an if-statement
end - terminate your program
endif - ends an if-statement
end sub - ends a subroutine definition
eof - check, if an open file contains data
eor() - compute the bitwise exclusive or of its two arguments
error - raise an error and terminate your program
euler - another name for the constant 2.71828182864
execute$() - execute a user defined subroutine, which must return a string
execute() - execute a user defined subroutine, which must return a number
exit - terminate your program
exp() - compute the exponential function of its single argument
export - mark a function as globally visible
else
Name
else - mark an alternative within an if-statement
Synopsis
if (...) then
...
else
...
endif
Description
The else-statement introduces the alternate branch of an if-statement. I.e.
it starts the sequence of statements, which is executed, if the condition of
the if-statement is not true.
Example
input "Please enter a number: " a
if (mod(a,2)=1) then
print a," is odd."
else
print a," is even."
endif
This program detects, if the number you have entered is even or odd.
See also
if
elsif
Name
elsif - starts an alternate condition within an if-statement
Synopsis
if (...) then
...
elseif (...)
...
elsif (...) then
...
else
...
endif
Description
The elsif-statement is used to select a single alternative among a series of
choices.
With each elsif-statement you may specify a condition, which is tested, if
the main condition (specified with the if-statement) has failed. Note that
elsif might be just as well written as elseif.
Within the example below, two variables a and b are tested against a range
of values. The variable a is tested with the elsif-statement. The very same
tests are performed for the variable b too; but here an involved series of
if-else-statements is employed, making the tests much more obscure.
Example
input "Please enter a number: " a
if (a<0) then
print "less than 0"
elseif (a<=10) then
print "between 0 and 10"
elsif (a<=20)
print "between 11 and 20"
else
print "over 20"
endif
input "Please enter another number: " b
if (b<0) then
print "less than 0"
else
if (b<=10) then
print "between 0 and 10"
else
if (b<=20) then
print "between 11 and 20"
else
print "over 20"
endif
endif
endif
Note, that the very same tests are performed for the variables a and b, but
can be stated much more clearly with the elsif-statement.
Note, that elsif might be written as elseif too, and that the keyword then
is optional.
See also
if, else
end
Name
end - terminate your program
Synopsis
end
Description
Terminate your program. Much (but not exactly) like the exit command.
Note, that end may not end your program immediately; if you have opened a
window or called clear screen, yabasic assumes, that your user wants to
study the output of your program after it has ended; therfore it issues the
line ---Program done, press RETURN--- and waits for a key to be pressed. If
you do not like this behaviour, consider using exit.
Example
print "Do you want to continue ?"
input "Please answer y(es) or n(o): " a$
if (lower$(left$(a$,1))="n") then
print "bye"
end
fi
See also
exit
endif
Name
endif - ends an if-statement
Synopsis
if (...) then
...
endif
Description
The endif-statement closes (or ends) an if-statement.
Note, that endif may be written in a variety of other ways: end if, end-if
or even fi.
The endif-statement must be omitted, if the if-statement does not contain
the keyword then (see the example below). Such an if-statement without endif
extends only over a single line.
Example
input "A number please: " a
if (a<10) then
print "Your number is less than 10."
endif
REM and now without endif
input "A number please: " a
if (a<10) print "Your number is less than 10."
See also
if
end sub
Name
end sub - ends a subroutine definition
Synopsis
sub foo(...)
...
end sub
Description
Marks the end of a subroutine-definition (which starts with the
sub-keyword). The whole concept of subroutines is explained within the entry
for sub.
Example
print foo(3)
sub foo(a)
return a*2
end sub
This program prints out 6. The subroutine foo simply returns twice its
argument.
See also
sub
eof
Name
eof - check, if an open file contains data
Synopsis
open 1,"foo.bar"
if (eof(1)) then
...
end if
Description
The eof-function checks, if there is still data left within an open file. As
an argument it expects the file-number as returned by (or used within) the
open-function (or statement).
Example
a=open("foo.bar")
while(not eof(a))
input #a,a$
print a$
end while
This example will print the contents of the file "foo.bar". The eof-function
will terminate the loop, if there is no more data left within the file.
See also
open
eor()
Name
eor() - compute the bitwise exclusive or of its two arguments
Synopsis
print eor(a,b)
Description
The eor-function takes two arguments and computes their bitwise exclusive
or. See your favorite introductory text on informatics for an explanation of
this function.
The xor-function is the same as the eor function; both are synonymous;
however they have each their own description, so you may check out the entry
of xor for a slightly different view.
Example
for a=0 to 3
for b=0 to 3
print fill$(bin$(a))," eor ",fill$(bin$(b))," = ",fill$(bin$(eor(a,b)))
next b
next a
sub fill$(a$)
return right$("0"+a$,2)
end sub
This example prints a table, from which you may figure, how the eor-function
is computed.
See also
and, or
error
Name
error - raise an error and terminate your program
Synopsis
error "Wrong, wrong, wrong !!"
Description
Produces the same kind or error messages, that yabasic itself produces (e.g.
in case of a syntax-error). The single argument is issued along with the
current line-number.
Example
input "Please enter a number between 1 and 10: " a
if (a<1 or a>10) error "Oh no ..."
This program is very harsh in checking the users input; instead of just
asking again, the program terminates with an error, if the user enters
something wrong.
The error message would look like this:
---Error in t.yab, line 2: Oh no ...
---Error: Program stopped due to an error
See also
Well, there should be a corresponding called warning; unfortunately ther is
none yet.
euler
Name
euler - another name for the constant 2.71828182864
Synopsis
foo=euler
Description
euler is the well known constant named after Leonard Euler; its value is
2.71828182864. euler is not a function, so parens are not allowed (i.e.
euler() will produce an error). Finally, you may not assign to euler; it
wouldn't sense anyway, because it is a constant.
Example
print euler
See also
pi
execute$()
Name
execute$() - execute a user defined subroutine, which must return a string
Synopsis
print execute$("foo$","arg1","arg2")
Description
execute$ can be used to execute a user defined subroutine, whose name may be
specified as a string expression.
This feature is the only way to execute a subroutine, whose name is not
known by the time you write your program. This might happen, if you want to
execute a subroutine, which is compiled (using the compile command) during
the course of execution of your program.
Note however, that the execute$-function is not the preferred method to
execute a user defined subroutine; almost all cases you should just execute
a subroutine by writing down its name within your yabasic program (see the
example).
Example
print execute$("foo$","Hello","world !")
sub foo$(a$,b$)
return a$+" "+b$
end sub
The example simply prints Hello world !, which is the return value of the
user defined subroutine foo$. The same could be achieved by executing:
print foo$(a$,b$)
See also
compile, execute
execute()
Name
execute() - execute a user defined subroutine, which must return a number
Synopsis
print execute("bar","arg1","arg2")
Description
The execute-function is the counterpart of the execute$-function (please see
there for some caveats). execute executes subroutines, which returns a
number.
Example
print execute("bar",2,3)
sub bar(a,b)
return a+b
end sub
See also
compile, execute$
exit
Name
exit - terminate your program
Synopsis
exit
exit 1
Description
Terminate your program and return any given value to the operating system.
exit is similar to end, but it will terminate your program immediately, no
matter what.
Example
print "Do you want to continue ?"
input "Please answer y(es) or n(o): " a$
if (lower$(left$(a$,1))="n") exit 1
See also
end
exp()
Name
exp() - compute the exponential function of its single argument
Synopsis
foo=exp(bar)
Description
This function computes e to the power of its argument, where e is the well
known euler constant 2.71828182864.
The exp-function is the inverse of the log-function.
Example
open window 100,100
for x=0 to 100
dot x,100-100*exp(x/100)/euler
next x
This program plots part of the exp-function, however the range is rather
small, so that you may not recognize the function from this plot.
See also
log
export
Name
export - mark a function as globally visible
Synopsis
export sub foo(bar)
end sub
Description
The export-statement is used within libraries to mark a user defined
subroutine as visible outside the library wherein it is defined.
Subroutines, which are not exported, must be qualified with the name of the
library, e.g. foo.baz (where foo is the name of the library and baz the name
of the subroutine); exported subroutines may be used without specifying the
name of the library, e.g. bar.
Therefore export may only be useful within libraries.
Example
The library foo.bar (which is listed below) defines two functions bar and
baz, however only the function bar is exported and therefore visible even
outside the library; baz is not exported and may only be used within the
library foo.yab:
export sub bar()
print "Hello"
end sub
sub baz()
print "World"
end sub
Now within your main program cux.yab (which imports the library foo.yab);
note that this program produces an error:
import foo
print "Calling subroutine foo.bar (okay) ..."
foo.bar()
print "done."
print "Calling subroutine bar (okay) ..."
bar()
print "done."
print "Calling subroutine foo.baz (okay) ..."
foo.baz()
print "done."
print "Calling subroutine baz (NOT okay) ..."
baz()
print "done."
The output when executing yabasic foo.yab is this:
Calling subroutine foo.bar (okay) ...
Hello
done.
Calling subroutine bar (okay) ...
Hello
done.
Calling subroutine foo.baz (okay) ...
World
done.
Calling subroutine baz (NOT okay) ...
---Error in main.yab, line 16: can't find subroutine 'baz'
---Dump: sub baz() called in main.yab,16
---Error: Program stopped due to an error
As the error message above shows, the subroutine baz must be qualified with
the name of the library, if used outside the library, wherein it is defined
(e.g. foo.baz. I.e. outside the library foo.yab you need to write foo.baz.
baz alone would be an error.
The subroutine bar (without adding the name of the library) however may (and
probably should) be used in any program, which imports the library foo.yab.
Note
In some sense the set of exported subroutines constitutes the interface of a
library.
See also
sub, import
F
Table of Contents
false - a constant with the value of 0
fi - another name for endif
fill - draw a filled circles, rectangles or triangles
for - starts a for-loop
frac() - return the fractional part of its numeric argument
false
Name
false - a constant with the value of 0
Synopsis
okay=false
Description
The constant false can be assigned to variables which later appear in
conditions (e.g. within an if-statement.
false may also be written as FALSE or even FaLsE.
Example
input "Please enter a number between 1 and 10: " a
if (check_input(a)) print "Okay"
sub check_input(x)
if (x>10 or x<1) return false
return true
end sub
The subroutine check_input checks its argument and returns true or false
according to the outcome of the check..
See also
true
fi
Name
fi - another name for endif
Synopsis
if (...)
fi
Description
fi marks the end of an if-statement and is exactly equivilent to endif,
please see there for further information.
Example
input "A number please: " a
if (a<10) then
print "Your number is less than 10."
fi
See also
endif
fill
Name
fill - draw a filled circles, rectangles or triangles
Synopsis
fill rectangle 10,10,90,90
fill circle 50,50,20
fill triangle 10,20,20,10,20,20
Description
The keyword fill may be used within the circle, rectangle or triangle
command and causes these shapes to be filled.
fill can be used in conjunction with and whereever the clear-clause may
appear. Used alone, fill will fill the interior of the shape (circle,
rectangle or triangle); together with clear the whole shape (including its
interior) is erased.
Example
open window 200,200
fill circle 100,100,50
clear fill rectangle 10,10,90,90
This opens a window and draws a pacman-like figure.
See also
clear, circle, rectangle, triangle
for
Name
for - starts a for-loop
Synopsis
for a=1 to 100 step 2
...
next a
Description
The for-loop lets its numerical variable (a in the synopsis) assume all
values within the given range. The optional step-clause may specify a value
(default: 1) by which the variable will be incremented (or decremented, if
step is negative).
Any for-statement can be replaced by a set of ifs and gotos; as you may
infer from the example below this is normally not feasable. However if you
want to know in detail how the for-statement works, you should study this
example, which presents a for-statement and an exactly equivilant series of
ifs and gotos.
Example
for a=1 to 10 step 2:print a:next
a=1
label check
if (a>10) goto done
print a
a=a+2
goto check
label done
This example simply prints the numbers 1, 3, 5, 7 and 9. It does this twice:
First with a simple for-statment and then with ifs and gotos.
See also
step, next
frac()
Name
frac() - return the fractional part of its numeric argument
Synopsis
x=frac(y)
Description
The frac-function takes its argument, removes all the digits to the left of
the comma and just returns the digits right of the comma, i.e. the
fractional part.
Refer to the example to learn how to rewrite frac by employing the
int-function.
Example
for a=1 to 10
print frac(sqr(a))
print sqr(a)-int(sqr(a))
next a
The example prints the fractional part of the square root of the numbers
between 1 and 10. Each result is computed (and printed) twice: Once by
employing the frac-function and once by employing the int-function.
See also
int
G
Table of Contents
getbit$() - return a string representing the bit pattern of a rectangle
within the graphic window
getscreen$() - returns a string representing a rectangular section of the
text terminal
glob() - check if a string matches a simple pattern
gosub - continue execution at another point within your program (and return
later)
goto - continue execution at another point within your program (and never
come back)
getbit$()
Name
getbit$() - return a string representing the bit pattern of a rectangle
within the graphic window
Synopsis
a$=getbit$(10,10,20,20)
a$=getbit$(10,10 to 20,20)
Description
The function getbit returns a string, which contains the encoded bit-pattern
of a rectangle within graphic window; the four arguments represent the
borders of the rectangle. The string returned might later be fed to the
putbit-command.
The getbit$-function might be used for simple animations (as in the example
below).
Example
open window 40,40
fill circle 20,20,18
circle$=getbit$(0,0,40,40)
close window
open window 200,200
for x=1 to 200
putbit circle$,x,80
next x
This example features a circle moving from left to right over the window.
See also
putbit
getscreen$()
Name
getscreen$() - returns a string representing a rectangular section of the
text terminal
Synopsis
a$=getscreen$(2,2,20,20)
Description
The getscreen$ function returns a string representing the area of the screen
as specified by its four arguments (which specify two corners). I.e.
everything you have printed within this rectangle will be encoded in the
string returned (including any colour-information).
Like most other commands dealing with advanced text output, getscreen$
requires, that you have called clear screen before.
Example
clear screen
for a=1 to 1000:
print color("red") "1";
print color("green") "2";
print color("blue") "3";
next a
screen$=getscreen$(10,10,40,10)
print at(10,10) " Please Press 'y' or 'n' ! "
a$=inkey$
putscreen screen$,10,10
This program fills the screen with coloured digits and afterwards asks the
user for a choice ( Please press 'y' or 'n' ! ). Afterwards the area of the
screen, which has been overwritten by the question will be restored with its
previous contents, whhch had been saved via getscreen$.
See also
putscreen$
glob()
Name
glob() - check if a string matches a simple pattern
Synopsis
if (glob(string$,pattern$)) ...
Description
The glob-function takes two arguments, a string and a (glob-) pattern, and
checks if the string matches the pattern. However glob does not employ the
powerful rules of regular expressions; rather it has only two special
characters: * (which matches any number (even zero) of characters) and ?
(which matches exactly a single character).
Example
for a=1 to 10
read string$,pattern$
if (glob(string$,pattern$)) then
print string$," matches ",pattern$
else
print string$," does not match ",pattern$
endif
next a
data "abc","a*"
data "abc","a?"
data "abc","a??"
data "abc","*b*"
data "abc","*"
data "abc","???"
data "abc","?"
data "abc","*c"
data "abc","A*"
data "abc","????"
This program checks the string abc against various patterns and prints the
result. The output is:
abc matches a*
abc does not match a?
abc matches a??
abc matches *b*
abc matches *
abc matches ???
abc does not match ?
abc matches *c
abc does not match A*
abc does not match ????
See also
There are no related commands.
gosub
Name
gosub - continue execution at another point within your program (and return
later)
Synopsis
gosub foo
label foo
return
Description
gosub remembers the current position within your program and then passes the
flow of execution to another point (which is normally marked with a label).
Later, when a return-statement is encountered, the execution is resumed at
the previous location.
gosub is the traditional command for calling code, which needs to be
executed from various places within your program. However, with subroutines
yabasic offers a much more flexible way to achieve this (and more).
Therefore gosub must to be considered obsolete.
Example
print "Do you want to exit ? "
gosub ask
if (r$="y") exit
label ask
input "Please answer yes or no, by typing 'y' or 'n': ",r$
return
See also
return, goto, sub, label, on gosub
goto
Name
goto - continue execution at another point within your program (and never
come back)
Synopsis
goto foo
label foo
Description
The goto-statement passes the flow of execution to another point within your
program (which is normally marked with a label).
goto is normally considered obsolete and harmful, however in yabasic it may
be put to the good use of leaving loops (e.g. while or for) prematurely.
Note however, that subroutines may not be left with the goto-statement.
Example
print "Please press any key to continue."
print "(program will continue by itself within 10 seconds)"
for a=1 to 10
if (inkey$(1)<>"") then goto done
next a
label done
print "Hello World !"
Here the goto-statment is used to leave the for-loop prematurely.
See also
gosub, on goto
H
Table of Contents
hex$() - convert a number into hexadecimal
hex$()
Name
hex$() - convert a number into hexadecimal
Synopsis
print hex$(foo)
Description
The hex$-function converts a number into a string with its hexadecimal
representation. hex$ is the inverse of the dec-function.
Example
open 1,"foo"
while(!eof(1))
print right$("0"+hex$(peek(1)),2)," ";
i=i+1
if (mod(i,10)=0) print
end while
print
This program reads the file foo and prints its output as a hex-dump using
the hex-function.
See also
decbin
I
Table of Contents
if - evaluate a condition and execute statements or not, depending on the
result
import - import a library
inkey$ - wait, until a key is pressed
input - read input from the user (or from a file) and assign it to a
variable
instr() - searches its second argument within the first; returns its
position if found
int() - return the integer part of its single numeric argument
if
Name
if - evaluate a condition and execute statements or not, depending on the
result
Synopsis
if (...) then
...
endif
if (...) ...
if (...) then
...
else
...
endif
if (...) then
...
elsif (...)
...
elsif (...) then
...
else
...
endif
Description
The if-statement is used to evaluate a conditions and take actions
accordingly. (As an aside, please note that there is no real difference
between conditions and expressions.)
There are two major forms of the if-statement:
* The one-line-form without the keyword then:
if (...) ...
This form evaluates the condition and if the result is true executes all
commands (seperated by colons) upt to the end of the line. There is
neither an endif keyword nor an else-branch.
* The multi-line-form with the keyword then:
if (...) then ... elsif (...) ... else ... endif
(where elsif and else are optional, whereas endif is not.
According to the requirements of your program, you may specify:
+ elsif(...), which specifies a condition, that will be evaluated only
if the condition(s) whithin if or any preceeding elsif did not
match.
+ else, which introduces a sequence of commands, that will be
executed, if none of the conditions above did match.
+ endif is required and ends the if-statement.
Example
input "Please enter a number between 1 and 4: " a
if (a<=1 or a>=4) error "Wrong, wrong !"
if (a=1) then
print "one"
elsif (a=2)
print "two"
elsif (a=3)
print "three"
else
print "four"
endif
The input-number between 1 and 4 is simply echoed as text (one, two, ...). The
example demonstrates both forms (short and long) of the if-statement (Note
however, that the same thing can be done, probably somewhat more elegant,
with the switch-statement).
See also
else, elsif, endif, conditions and expressions.
import
Name
import - import a library
Synopsis
import foo
Description
The import-statment imports a library. It expects a single argument, which
must be the name of a library (without the trailing .yab). This library will
then be read and parsed and its subroutines (and variables) will be made
available within the main program.
Libraries will first be searched within the current directory (i.e. the
directory within which you have invoked yabasic), then within a special
directory, whose exact location depends on your system. Typical values would
be /usr/lib under Unix or C:\yabasic\lib under Windows. However only yabasic-help-usage may tell the truth. The location of this second directory may be
changed with the option -library (either under Windows or Unix).
Example
Lets say you have a yabasic-program foo.yab, which imports a library
lib.yab. foo.yab reads:
import lib
rem This works ...
lib.x(0)
rem This works too ..
x(1)
rem And this.
lib.y(2)
rem But this not !
y(3)
Now the library lib.yab reads:
rem Make the subroutine x easily available outside this library
export sub x(a)
print a
return
end sub
rem sub y must be referenced by its full name
rem outside this library
sub y(a)
print a
return
end sub
This program produces an error:
0
1
2
---Error in foo.yab, line 13: can't find subroutine 'y'
---Dump: sub y() called in foo.yab,13
---Error: Program stopped due to an error
As you may see from the error message, yabasic is unable to find the
subroutine y without specifying the name of the library (i.e. lib.y). The
reason for this is, that y, other than x, is not exported from the library
lib.yab (using the export-statement).
See also
export, sub
inkey$
Name
inkey$ - wait, until a key is pressed
Synopsis
clear screen
foo$=inkey$
inkey$
foo$=inkey$(bar)
inkey$(bar)
Description
The inkeys$-function waits, until the user presses a key on the keyboard or
a button of his mouse, and returns this very key. An optional argument
specifies the number of seconds to wait; if omitted, inkey$ will wait
indefinitely.
inkey$ may only be used, if clear screen has been called at least once.
For normal keys, yabasic simply returns the key, e.g. a, 1 or !. For
function keys you will get f1, f2 and so on. Other special keys will return
these strings respectively: enter, backspace, del, esc, scrnup (for screen
up), scrndown and tab. Modifier keys (e.g. ctrl, alt or shift) by themself
can not be detected (however, if you press shift and e.g. a simultaniously,
inkey$ will return the letter A instead of a of course).
If a graphical window has been opened (via open window) any mouseclick
within this window will be returned by inkey$ too. The string returned (e.g.
MB1d+0:0028,0061, MB2u+0:0028,0061 or MB1d+1:0028,0061) is constructed as
follows:
* Every string associated with a mouseclick will start with the fixed
string MB
* The next digit (1, 2 or 3) specifies the mousebutton pressed.
* A single letter, d or u, specifies, if the mousebutton has been pressed
or released: d stands for down, i.e. the mousebutton has been pressed; u
means up, i.e. the mousebutton has been released.
* The plus-sign ('+'), which follows is always fixed.
* The next digit (in the range 0 to 7) encodes the modifier keys pressed,
where 1 stands for shift, 2 stands for alt and 4 stands for ctrl.
* The next four digits (e.g. 0028) contain the x-position, where the
mousebutton has been pressed.
* The comma to follow is always fixed.
* The last four digits (e.g. 0061) contain the y-position, where the
mousebutton has been pressed.
All those fields are of fixed length, so you may use functions like mid$ to
extract certain fields. However, note that with mousex, mousey, mouseb and
mousemod there are specialized functions to return detailed information
about the mouseclick. Finally it should be noted, that inkey$ will only
register mouseclicks within the graphic-window; mouseclicks in the
text-window cannot be detected.
inkey$ accepts an optional argument, specifying a timeout in seconds; if no
key has been pressed within this span of time, an empty string is returned.
If the timeout-argument is omitted, inkey$ will wait for ever.
Example
clear screen
open window 100,100
print "Press any key or press 'q' to stop."
repeat
a$=inkey$
print a$
until(a$="q")
This program simply returns the key pressed. You may use it, to learn, which
strings are returned for the special keys on your keyboard (e.g.
function-keys).
See also
clear screen,mousex, mousey, mouseb, mousemod
input
Name
input - read input from the user (or from a file) and assign it to a
variable
Synopsis
input a
input a,b,c
input a$
input "Hello" a
input #1 a$
Description
input reads the new contents of one or many (numeric- or string-) variables,
either from the keyboard (i.e. from you) or from a file. An optional first
string-argument specifies a prompt, which will be issued before reading any
contents.
If you want to read from an open file, you need to specify a hash ('#'),
followed by the number, under which the file has been opened.
Note, that the input is split at spaces, i.e. if you enter a whole line
consisting of many space-seperated word, the first input-statement will only
return the first word; the other words will only be returned on subsequent
calls to input; the same applies, if a single input reads multiple
variables: The first variable gets only the first word, the second one the
second word, and so on. If you don't like this behaviour, you may use line
input, which returns a whole line (including embedded spaces) at once.
Example
input "Please enter the name of a file to read: " a$
open 1,a$
while(!eof(1))
input #1 b$
print b$
wend
If this program is stored within a file test.yab and you enter this name
when prompted for a file to read, you will see this output:
Please enter the name of a file to read: t.yab
input
"Please
enter
the
name
of
a
file
to
read:
"
a$
open
1,a$
while(!eof(1))
input
#1
b$
print
b$
wend
See also
line input
instr()
Name
instr() - searches its second argument within the first; returns its
position if found
Synopsis
print instr(a$,b$)
if (instr(a$,b$)) ...
pos=instr(a$,b$,x)
Description
The instr-functions requires two string arguments and searches the second
argument within the first. If the second argument can be found within the
first, the position is returned (counting from one). If it can not be found,
the instr-function returns 0; this makes this function usable within the
condition of an if-statement (see the example below).
If you supply a third, numeric argument to the instr-function, it will be
used as a starting point for the search. Therefore
instr("abcdeabcdeabcde","e",8) will return 10, because the search for an "e"
starts at position 8 and finds the "e" at position 10 (and not the one at
position 5).
Example
input "Please enter a text containing the string 'bumf': " a$
if (instr(a$,"bumf")) then
print "Well done !"
else
print "not so well ..."
endif
See also
rinstr
int()
Name
int() - return the integer part of its single numeric argument
Synopsis
print int(a)
Description
The int-function returns only the digits before the comma; int(2.5) returns
2 and int(-2.3) returns -2.
Example
input "Please enter a whole number between 1 and 10: " a
if (a=int(a) and a>=1 and a<=10) then
print "Thanx !"
else
print "Never mind ..."
endif
See also
frac
L
Table of Contents
label - mark a specific location within your program for goto, gosub or
restore
left$() - return (or change) left end of a string
len() - return the length of a string
line - draw a line
line input - read in a whole line of text and assign it to a variable
local - mark a variable as local to a subroutine
log() - compute the natural logarithm
loop - marks the end of an infinite loop
lower$() - convert a string to lower case
ltrim$() - trim spaces at the left end of a string
label
Name
label - mark a specific location within your program for goto, gosub or
restore
Synopsis
label foo
goto foo
Description
The label-command can be used to give a name to a specific location within
your program. Such a position might be referred from one of three commands:
goto, gosub and restore.
You may use labels safely within libraries, because a label (e.g. foo) does
not collide with a label with the same name within the main program or
within another library; yabasic will not mix them up.
As an aside, please note, that line numbers are a special (however
deprecated) case of labels; see the second example below.
Example
for a=1 to 100
if (rand(10)>5) goto done
next a
label done
10 for a=1 to 100
20 if (rand(10)>5) goto 40
30 next a
40
Within this example, the for-loop will probably be left prematurely with a
goto-statement. This task is done twice: First with labels and then again
with line numbers.
See also
gosub, goto.
left$()
Name
left$() - return (or change) left end of a string
Synopsis
print left$(a$,2)
left$(b$,3)="foobar"
Description
The left$-function accepts two arguments (a string and a number) and returns
the part from the left end of the string, whose length is specified by its
second argument. Loosely spoken, it simply returns the requested number of
chars from the left end of the given string.
Note, that the left$-function can be assigned to, i.e. it may appear on the
left hand side of an assignment. In this way it is possible to change a part
of the variable used within the left$-function. Note, that that way the
length of the string cannot be changed, i.e. characters might be
overwritten, but not added. For an example see below.
Example
input "Please answer yes or no: " a$
l=len(a$):a$=lower$(a$):print "Your answer is ";
if (left$("yes",l)=a$ and l>=1) then
print "yes"
elsif (left$("no",l)=a$ and l>=1) then
print "no"
else
print "?"
endif
This example asks a simple yes/no question and goes some way to accept even
incomplete input, while still beeing able to reject invalid input.
This second example demonstrates the capability to assign to the
left$-function.
a$="Heiho World !"
print a$
left$(a$,5)="Hello"
print a$
See also
right$, mid$
len()
Name
len() - return the length of a string
Synopsis
x=len(a$)
Description
The len-function returns the length of its single string argument.
Example
input "Please enter a password: " a$
if (len(a$)<6) error "Password too short !"
This example checks the length of the password, that the user has entered.
See also
left$, right$ and mid$,
line
Name
line - draw a line
Synopsis
open window 100,100
line 0,0,100,100
line 0,0 to 100,100
new curve
line 100,100
line to 100,100
open window 100,100
clear line 0,0,100,100
clear line 0,0 to 100,100
new curve
clear line 100,100
clear line to 100,100
Description
The line-command draws a line. Simple as this is, the line-command has a
large variety of forms as they are listed in the synopsis above. Lets look
at them a little closer:
* A line has a starting and an end point; therefore the line-command
(normally) needs four numbers as arguments, representing these two
points. This is the first form appearing within the synopsis.
* You may seperate the two points with either ',' or to, which accounts
for the second form of the line-command.
* The line-command may be used to draw a connected sequence of lines with
a sequence of commands like line x,y; Each command will draw a line from
the point where the last line-command left off, to the point specified
in the arguments. Note, that you need to use the command new curve
before you may issue such a line-command. See the example below.
* You may insert the word to for beauty: line to x,y, which does exactly
the same as line x,y
* Finally, you may choose not to draw, but to erase the lines; this can be
done by prepending the phrase clear. This account for all the other
forms of the line-command.
Example
open window 200,200
line 10,10 to 10,190
line 10,190 to 190,190
new curve
for a=0 to 360
line to 10+a*180/360,100+60*sin(a*pi/180)
next a
This example draws a sine-curve (with an offset in x- and y-direction).
Note, that the first line-command after new curve does not draw anything.
Only the coordinates will be stored. The second iteration of the loop then
uses these coordinates as a starting point for the first line.
See also
new curve, close curve, open window
line input
Name
line input - read in a whole line of text and assign it to a variable
Synopsis
line input a
line input a$
line input "Hello" a
line input #1 a$
Description
In most respects line input is like the input-command: It reads the new
contents of a variable, either from keyboard or from a file. However, line
input always reads a complete line and assigns it to its variable. line
input does not stop reading at spaces and is therefore the best way to read
in a string which might contain whitespace. Note, that the final newline is
stripped of.
Example
line input "Please enter your name (e.g. Frodo Beutelin): " a$
print "Hello ",a$
Note that the usage of line input is essential in this example; a simple
input-statement would only return the string up to the first space, e.g.
Frodo.
See also
input
local
Name
local - mark a variable as local to a subroutine
Synopsis
sub foo()
local a,b,c$,d(10),e$(5,5)
...
end sub
Description
The local-command can (and should be) used to mark a variable (or array) as
local to the containing subroutine. This means, that a local variable in
your subroutine is totally different from a variable with the same name
within your main program. Variables which are known everywhere within your
program are called global in contrast.
Declaring variables within the subroutine as local helps to avoid hard to
find bugs; therefore local variables should be used whenever possible.
Note, that the parameters of your subroutines are always local.
As you may see from the example, local arrays may be created without using
the keyword dim (which is required only for global arrays).
Example
a=1
b=1
print a,b
foo()
print a,b
sub foo()
local a
a=2
b=2
end sub
This example demonstrates the difference between local and global variables;
it produces this output:
1 1
1 2
As you may see, the content of the global variable a is unchanged after the
subroutine foo; this is because the assignment a=2 within the subroutine
affects the local variable a only and not the global one. However, the
variable b is never declared local and therefore the subroutine changes the
global variable, which is reflected in the output of the second
print-statement.
See also
sub, static, dim
log()
Name
log() - compute the natural logarithm
Synopsis
a=log(x)
a=log(x,base)
Description
The log-function computes the logarithm of its first argument. The optional
second argument gives the base for the logarithm; if this second argument is
omitted, the euler-constant 2.71828... will be taken as the base.
Example
open window 200,200
for x=10 to 190 step 10:for y=10 to 190 step 10
r=3*log(1+x,1+y)
if (r>10) r=10
if (r<1) r=1
fill circle x,y,r
next y:next x
This draws another nice plot.
See also
exp
loop
Name
loop - marks the end of an infinite loop
Synopsis
do
...
loop
Description
The loop-command marks the ends of a loop (which is started by do), wherein
all statements within the loop are repeated forever. In this respect the do
loop-loop is infinite, however, you may leave it anytime via break or goto.
Example
print "Hello, I will throw dice, until I get a 2 ..."
do
r=int(rand(6))+1
print r
if (r=2) break
loop
See also
do, for, repeat, while, break
lower$()
Name
lower$() - convert a string to lower case
Synopsis
l$=lower$(a$)
Description
The lower$-function accepts a single string-argument and converts it to all
lower case.
Example
input "Please enter a password: " a$
if (a$=lower$(a$)) error "Your password is NOT mixed case !"
This example prompts for a password and checks, if it is really lower case.
See also
upper$
ltrim$()
Name
ltrim$() - trim spaces at the left end of a string
Synopsis
a$=ltrim$(b$)
Description
The ltrim$-function removes all whitespace from the left end of a string and
returns the result.
Example
input "Please answer 'yes' or 'no' : " a$
a$=lower$(ltrim$(rtrim$(a$)))
if (len(a$)>0 and a$=left$("yes",len(a$))) then
print "Yes ..."
else
print "No ..."
endif
This example prompts for an answer and removes any spaces, which might
precede the input; therefore it is even prepared for the (albeit somewhat
patological case, that the user first hits space before entering his answer.
See also
rtrim$, trim$
M
Table of Contents
max() - return the larger of its two arguments
mid$() - return (or change) characters from within a string
min() - return the smaller of its two arguments
mod() - compute the remainder of a division
mouseb - extract the state of the mousebuttons from a string returned by
inkey$
mousemod - return the state of the modifier keys during a mouseclick
mousex - return the x-position of a mouseclick
mousey - return the y-position of a mouseclick
max()
Name
max() - return the larger of its two arguments
Synopsis
print max(a,b)
Description
Return the maximum of its two arguments.
Example
dim m(10)
for a=1 to 1000
m=0
For b=1 to 10
m=max(m,ran(10))
next b
m(m)=m(m)+1
next a
for a=1 to 9
print a,": ",m(a)
next a
Within the inner for-loop (the one with the loop-variable b), the example
computes the maximum of 10 random numbers. The outer loop (with the loop
variable a) now repeats this process 1000 times and counts, how often each
maximum appears. The last loop finally reports the result.
Now, the interesting question would be, which will be approached, when we
increase the number of iterations from thousend to infinity. Well, maybe
someone could just tell me :-)
See also
min
mid$()
Name
mid$() - return (or change) characters from within a string
Synopsis
print mid$(a$,2,1)
print mid$(a$,2)
mid$(a$,5,3)="foo"
mid$(a$,5)="foo"
Description
The mid$-function requires three arguments: a string and two numbers, where
the first number specifies a position within the string and the second one
gives the number of characters to be returned; if you omit the second
argument, the mid$-function returns all characters up to the end of the
string.
Note, that you may assign to the mid$-function, i.e. mid$ may appear on the
left hand side of an assignment. In this way it is possible to change a part
of the variable used within the mid$-function. Note, that that way the
length of the string cannot be changed, i.e. characters might be
overwritten, but not added. For an example see below.
Example
input "Please enter a string: " a$
for a=1 to len(a$)
if (instr("aeiou",lower$(mid$(a$,a,1)))) mid$(a$,a,1)="e"
next a
print "When you turn everything to lower case and"
print "replace every vowel with 'e', your input reads:"
print
print a$
This example transforms the input string a bit, using the mid$-function to
retrieve a character from within the string as well as to change it.
See also
left$ and right$.
min()
Name
min() - return the smaller of its two arguments
Synopsis
print min(a,b)
Description
Return the minimum of its two argument.
Example
dim m(10)
for a=1 to 1000
m=min(ran(10),ran(10))
m(m)=m(m)+1
next a
for a=1 to 9
print a,": ",m(a)
next a
For each iteration of the loop, the lower of two random number is recorded.
The result is printed at the end.
See also
max
mod()
Name
mod() - compute the remainder of a division
Synopsis
print mod(a,b)
Description
The mod-function divides its two arguments and computes the remainder. Note,
that a/b-int(a/b) and mod(a,b) are always equal.
Example
clear screen
print at(10,10) "Please wait ";
p$="-\|/"
for a=1 to 100
rem ... do something lengthy here, or simply sleep :-)
pause(1)
print at(22,10) mid$(p$,1+mod(a,4))
next a
This example executes some time consuming action within a loop (in fact, it
simply sleeps) and gives the user some indication of progress by displaying
a turning bar (thats where the mod()-function comes into play).
See also
int, frac
mouseb
Name
mouseb - extract the state of the mousebuttons from a string returned by
inkey$
Synopsis
inkey$
print mouseb()
print mouseb
a$=inkey$
print mouseb(a$)
Description
The mouseb-function is a helper function for decoding part of the (rather
complicated) strings, which are returned by the inkey$-function. If a
mousebutton has been pressed, the mouseb-function returns the number (1,2 or
3) of the mousebutton, when it is pressed and returns its negative (-1,-2 or
-3), when it is released.
The mouseb-function accepts zero or one arguments. A single argument should
be a string returned by the inkey$-function; if mouseb is called without any
arguments, it returns the values from the last call to inkey$, which are
stored implicitly and internally by yabasic.
Note
Note however, that the value returned by the mouseb-function does not
reflect the current state of the mousebuttons. It rather extracts the
information from the string passed as an argument (or from the last call to
the inkey$-function, if no argument is passed). So the value returned by
mouseb reflects the state of the mousebuttons at the time the
inkey$-function has been called; as opposed to the time the mouseb-function
is called.
Example
open window 200,200
clear screen
print "Please draw lines; press (and keep it pressed)"
print "the left mousebutton for the starting point,"
print "release it for the end-point."
do
if (mouseb(release$)=1) press$=release$
release$=inkey$
if (mouseb(release$)=-1) then
line mousex(press$),mousey(press$) to mousex(release$),mousey(release$)
endif
loop
This is a maybe the most simplistic line-drawing program possible, catching
presses as well as releases of the first mousebutton.
See also
inkey$, mousex, mousey and mousemod
mousemod
Name
mousemod - return the state of the modifier keys during a mouseclick
Synopsis
inkey$
print mousemod()
print mousemod
a$=inkey$
print mousemod(a$)
Description
The mousemod-function is a helper function for decoding part of the (rather
complicated) strings, which are returned by the inkey$-function if a
mousebutton has been pressed. It returns the state of the keyboard modifiers
(shift, ctrl or alt): If the shift-key is pressed, mousemod returns 1, for
the alt-key 2 and for the ctrl-key 4. If more than one key is pressed, the
sum of these values is returned, e.g. mousemod returns 5, if shift and ctrl
are pressed simultanously.
The mousemod-function accepts zero or one arguments. A single argument
should be a string returned by the inkey$-function; if mousemod is called
without any arguments, it returns the values from the last call to inkey$
(which are stored implicitly and internally by yabasic).
Note
Please see also the Note within the mouseb-function.
Example
open window 200,200
clear screen
do
a$=inkey$
if (left$(a$,2)="MB") then
x=mousex(a$)
y=mousey(a$)
if (mousemod(a$)=0) then
circle x,y,20
else
fill circle x,y,20
endif
endif
loop
This program draws a circle, whenever a mousebutton is pressed; the circles
are filled, when any modifier is pressed, and empty if not.
See also
inkey$, mousex, mousey and mouseb
mousex
Name
mousex - return the x-position of a mouseclick
Synopsis
inkey$
print mousex()
print mousex
a$=inkey$
print mousex(a$)
Description
The mousex-function is a helper function for decoding part of the (rather
complicated) strings, which are returned by the inkey$-function; It returns
the x-position of the mouse as encoded within its argument.
The mousex-function accepts zero or one arguments. A single argument should
be a string returned by the inkey$-function; if mousex is called without any
arguments, it returns the values from the last call to inkey$ (which are
stored implicitly and internally by yabasic).
Note
Please see also the Note within the mouseb-function.
Example
open window 200,200
clear screen
do
a$=inkey$
if (left$(a$,2)="MB") then
line mousex,0 to mousex,200
endif
loop
This example draws vertical lines at the position, where the mousebutton has
been pressed.
See also
inkey$, mousemod, mousey and mouseb
mousey
Name
mousey - return the y-position of a mouseclick
Synopsis
inkey$
print mousey()
print mousey
a$=inkey$
print mousey(a$)
Description
The mousey-function is a helper function for decoding part of the (rather
complicated) strings, which are returned by the inkey$-function. mousey
returns the y-position of the mouse as encoded within its argument.
The mousey-function accepts zero or one arguments. A single argument should
be a string returned by the inkey$-function; if mousey is called without any
arguments, it returns the values from the last call to inkey$ (which are
stored implicitly and internally by yabasic).
Note
Please see also the Note within the mouseb-function.
Example
open window 200,200
clear screen
do
a$=inkey$
if (left$(a$,2)="MB") then
line 0,mousey to 200,mousey
endif
loop
This example draws horizontal lines at the position, where the mousebutton
has been pressed.
See also
inkey$, mousemod, mousex and mouseb
N
Table of Contents
new curve - start a new curve, that will be drawn with the line-command
next - mark the end of a for loop
not - negate an expression; can be written as !
numparams - return the number of parameters, that have been passed to a
subroutine
new curve
Name
new curve - start a new curve, that will be drawn with the line-command
Synopsis
new curve
line to x,y
Description
The new curve-function starts a new sequence of lines, that will be drawn by
repeated line to-commands.
Example
open window 200,200
ellipse(100,50,30,60)
ellipse(150,100,60,30)
sub ellipse(x,y,xr,yr)
new curve
for a=0 to 2*pi step 0.2
line to x+xr*cos(a),y+yr*sin(a)
next a
close curve
end sub
This example defines a subroutine ellipse that draws an ellipse. Within this
subroutine, the ellipse is drawn as a sequence of lines started with the new
curve command and closed with close curve.
See also
line, close curve
next
Name
next - mark the end of a for loop
Synopsis
for a=1 to 10
next a
Description
The next-keyword marks the end of a for-loop. All statements up to the
next-keyword will be repeated as specified with the for-clause. Note, that
the name of the variable is optional; so instead of next a you may write
next.
Example
for a=1 to 300000
for b=1 to 21+20*sin(pi*a/20)
print "*";
next b
print
sleep 0.1
next a
This example simply plots a sine-curve until you fall asleep.
See also
for
not
Name
not - negate an expression; can be written as !
Synopsis
if (not a<b) then ...
bad=!okay
Description
The keyword not (or ! for short) is mostly used within conditions (e.g.
within if- or while-statements). There it is employed to negate the
condition or expression (i.e. turn TRUE into FALSE and vice versa)
However not can be used within arithmetic calculations too., simply because
there is no difference between arithmetic and logical expressions.
Example
input "Please enter three ascending numbers: " a,b,c
if (not (a<b and b<c)) error " the numbers you have entered are not ascending .
See also
and,or
numparams
Name
numparams - return the number of parameters, that have been passed to a
subroutine
Synopsis
sub foo(a,b,c)
if (numparams=1) ...
...
end sub
Description
Within a subroutine the local variable numparam or numparams contains the
number of parameters, that have been passed to the subroutine. This
information can be useful, because the subroutine may have been called with
fewer parameters than actually declared. The number of values that actually
have been passed while calling the subroutine, can be found in numparams.
Note, that arguments which are used in the definition of a subroutine but
are left out during a call to it (thereby reducing the value of numparams)
receive a value of 0 or "" (empty string) respectively.
Example
a$="123456789"
print part$(a$,4)
print part$(a$,3,7)
sub part$(a$,f,t)
if (numparams=2) then
return mid$(a$,f)
else
return mid$(a$,f,t-f+1)
end if
end sub
When you run this example, it will print 456789 and 34567. Take a look at
the subroutine part$, which returns part of the string which has been passed
as an argument. If (besides the string) two numbers are passed, they define
the starting and end position of the substring, that will be returned.
However, if only one number is passed, the rest of the string, starting from
this position will be returned. Each of these cases is recognized with the
help of the numparams variable.
See also
sub
O
Table of Contents
on gosub - jump to one of multiple gosub-targets
on goto - jump to one of many goto-targets
on interrupt - change reaction on keyboard interrupts
open - open a file
open printer - open printer for printing graphics
open window - open a graphic window
logical or - logical or, used in conditions
or() - arithmetic or, used for bit-operations
on gosub
Name
on goto - jump to one of multiple gosub-targets
Synopsis
on a gosub foo,bar,baz
...
label foo
...
return
label bar
...
return
label baz
...
return
Description
The on gosub statement uses its numeric argument (the one between on and
gosub) to select an element from the list of labels, which follows after the
gosub-keyword: If the number is 1, the program does a gosub to the first
label; if the number is 2, to the second and, so on. if the number is zero
or less, the program continues at the position of the first label; if the
number is larger than the total count of labels, the execution continues at
the position of the last label; i.e. the first and last label in the list
constitute some kind of fallback-slot.
Note, that the on gosub-command can no longer be considered state of the
art; people (not me !) may even start to mock you, if you use it.
Example
do
print "Please enter a number between 1 and 3: "
print
input "Your choice " a
on a gosub bad,one,two,three,bad
loop
label bad
print "No. Please between 1 and 3"
return
label one
print "one"
return
label two
print "two"
return
label three
print "three"
return
Note, how invalid input (a number less than 1, or larger than 3) is
automatically detected.
See also
goto, on gosub/function>
on goto
Name
on goto - jump to one of many goto-targets
Synopsis
on a goto foo,bar,baz
...
label foo
...
label bar
...
label baz
...
Description
The on goto statement uses its numeric argument (the one between on and goto
to select an element from the list of labels, which follows after the
goto-keyword: If the number is 1, the execution continues at the first
label; if the number is 2, at the second, and so on. if the number is zero
or less, the program continues at the position of the first label; if the
number is larger than the total count of labels, the execution continues at
the position of the last label; i.e. the first and last label in the list
constitute some kind of fallback-slot.
Note, that (unlike the goto-command) the on goto-command can no longer be
considered state of the art; people may (not me !) even start to mock you,
if you use it.
Example
label over
print "Please Select one of these choices: "
print
print " 1 -- show time"
print " 2 -- show date"
print " 3 -- exit"
print
input "Your choice " a
on a goto over,show_time,show_date,terminate,over
label show_time
print time$()
goto over
label show_date
print date$()
goto over
label terminate
exit
Note, how invalid input (a number less than 1, or larger than 3) is
automatically detected; in such a case the question is simply issued again.
See also
goto, on gosub/function>
on interrupt
Name
on interrupt - change reaction on keyboard interrupts
Synopsis
on interrupt break
on interrupt continue
Description
With the on interrupt-command you may change the way, how yabasic reacts on
a keyboard interrupt; it comes in two variants: on interrupt break and on
interrupt continue. A keyboard interrupt is produced, if you press ctrl-C on
your keyboard; normally (and certainly after you have called on interrupt
break), yabasic will terminate with an error message. However after the
command on interrupt continue yabasic ignores any keyboard interrupt. This
may be useful, if you do not want your program beeing interruptible during
certain critical operations (e.g. updating of files).
Example
print "Please stand by while writing a file with random data ..."
on interrupt continue
open "random.data" for writing as #1
for a=1 to 100
print #1 ran(100)
print a," percent done."
sleep 1
next a
close #1
on interrupt continue
This program writes a file with 100 random numbers. The on interrupt
continue command insures, that the program will not be terminated on a
keyboard interrupt and the file will be written entirely in any case. The
sleep-command just stretches the process arificially to give you a chance to
try a ctrl-C.
See also
There is no related command.
open
Name
open - open a file
Synopsis
open a,"file","r"
open #a,"file","w"
open #a,printer
open "file" for reading as a
open "file" for writing as #a
a=open("file")
a=open("file","r")
if (open(a,"file")) ...
if (open(a,"file","w")) ...
Description
The open-command opens a file for reading or writing or a printer for
printing text. open comes in a wide variety of ways; it requires these
arguments:
filenumber
In the synopsis this is a or #a. In yabasic each file is associated
with a number between 1 and a maximum value, which depends on the
operating system. For historical reasons the filenumber can be
preceded by a hash ('#'). Note, that specifying a filenumber is
optional; if it is omitted, the open-function will return a
filenumber, which should then be stored in a variable for later
reference. This filenumber can be a simple number or an arbitrary
complex arithmetic expression, in which case braces might be
necessary to save yabasic from getting confused.
filename
In the synopsis above this is "file". This string specifies the name
of the file to open (note the important caveat on specifying these
filenames).
accessmode
In the synopsis this is "r", "w", for reading or for writing. This
string or clause specifies the mode in which the file is opened; it
may be one of:
"r"
Open the file for reading (may also be written as for reading).
If the file does not exist, the command will fail. This mode is
the default, i.e. if no mode is specified with the
open-command, the file will be opened with this mode.
"w"
Open the file for writing (may also be written as for writing).
If the file does not exist, it will be created.
"a"
Open the file for appending, i.e. what you write to the file
will be appended after its initial contents. If the file does
not exist, it will be created.
"b"
This letter may not appear alone, but may be combined with the
other letters (e.g. "rb") to open a file in binary mode (as
opposed to text mode).
As you may see from the synopsis, the open-command may either be called as a
command (without braces) or as a function (with braces). If called as a
function, it will return the filenumber or zero if the operation fails.
Therefore the open-function may be used within the condition of an
if-statement.
If the open-command fails, you may use peek("error") to retrieve the exact
nature of the error.
Furthermore note, that there is another, somewhat separate usage of the
open-command; if you specify the bareword printer instead of a filename, the
command opens a printer for printing text. Every text (and only text) you
print to this file will appear on your printer. Note, that this is very
different from printing graphics, as can be done with open printer.
Finally you may read the description for peek("error") to learn which errors
may have happened during an open-call.
Example
open "foo.bar" for writing as #1
print #1 "Hallo !"
close #1
if (not open(1,"foo.bar")) error "Could not open 'foo.bar' for reading"
while(not eof(1))
line input #1 a$
print a$
wend
This example simply opens the file foo.bar, writes a single line, reopens it
and reads its contents again.
See also
close, print, peek, peek("error") and open printer
open printer
Name
open printer - open printer for printing graphics
Synopsis
open printer
open printer "file"
Description
The open printer-command opens a printer for printing graphics. The command
requires, that a graphic window has been opened before. Everything that is
drawn into this window will then be sent to the printer too.
A new piece of paper may be started with the clear window-command; the final
(or only) page will appear after the close printer-command.
Note, that you may specify a filename with open printer; in that case the
printout will be sent to a filename instead to a printer. Your program or
the user will be responsible for sending this file to the printer
afterwards.
If you use yabasic under Unix, you will need a postscript printer (because
yabasic produces postscript output). Alternatively you may use ghostscript
to transfrom the postscript file into a form suitable for your printer; but
that is beyond the responsibility of yabasic.
Example
open window 200,200
open printer
line 0,0 to 200,200
text 100,100,"Hallo"
close window
close printer
This example will open a window, draw a line and print some text within;
everything will appear on your printer too.
See also
close printer
open window
Name
open window - open a graphic window
Synopsis
open window x,y
open window x,y,"font"
Description
The open window-command opens a window of the specified size. Only one
window can be opened at any given moment of time.
An optional third argument specifies a font to be used for any text within
the window. It can however be changed with any subsequent text-command.
Example
for a=200 to 400 step 10
open window a,a
for b=0 to a
line 0,b to a,b
line b,0 to b,a
sleep 0.1
close window
next a
See also
close window, text
logical or
Name
or - logical or, used in conditions
Synopsis
if (a or b) ...
while (a or b) ...
Description
Used in conditions (e.g within if or while) to join two expressions. Returns
true, if either its left or its right or both arguments are true; returns
false otherwise.
Example
input "Please enter a number"
if (a>9 or a<1) print "a is not between 1 and 9"
See also
and,not
or()
Name
or() - arithmetic or, used for bit-operations
Synopsis
x=or(a,b)
Description
Used to compute the bitwise or of both its argument. Both arguments are
treated as binary numbers (i.e. a series of 0 and 1); a bit of the resulting
value will then be 1, if any of its arguments has 1 at this position in
their binary representation.
Note, that both arguments are silently converted to integer values and that
negative numbers have their own binary representation and may lead to
unexpected results when passed to or.
Example
print or(14,3)
This will print 15. This result is clear, if you note, that the binary
representation of 14 and 3 are 1110 and 0011 respectively; this will yield
1111 in binary representaion or 15 as decimal.
See also
oand, eor and not
P
Table of Contents
pause - pause, sleep, wait for the specified number of seconds
peek - retrieve various internal informations
peek$ - retrieve various internal string-informations
pi - a constant with the value 3.14159
poke - change selected internals of yabasic
print - Write to terminal or file
print color - print with color
print colour - see color
putbit - draw a rectangle of pixels encoded within a string into the
graphics window
putscreen - draw a rectangle of characters into the text terminal
pause
Name
pause - pause, sleep, wait for the specified number of seconds
Synopsis
pause 5
Description
The pause-command has many different names: You may write pause, sleep or
wait interchangable; whatever you write, yabasic will always do exactly the
same.
The pause-command will simply wait for the specified number of seconds. This
may be a fractional number, so you may well wait less than a second.
However, if you try to pause for a smaller and smaller interval (e.g. 0.1
seconds, 0.01 seconds, 0.001 seconds and so on) you will find that at some
point yabasic will not wait at all. The minimal interval that can be waited
depends on the system (Unix, Windows) you are using.
The pause-command cannot be interrupted. However, sometimes you may want the
wait to be interuptible by simply pressing a key on the keyboard. In such
cases you should consider using the inkey$-function, with a number of
seconds as an argument).
Example
deg=0
do
maxx=44+40*sin(deg)
for x=1 to maxx
print "*";
next x
pause 0.1+(maxx*maxx/(4*84*84))
print
deg=deg+0.1
loop
This example draws a sine-curve; due to the pause-statement the speed of
drawing varies in the same way as the speed of a ball might vary, if it
would roll along this curve under the influence of gravity.
See also
sleep, wait
peek
Name
peek - retrieve various internal informations
Synopsis
print peek("foo")
a=peek(#1)
Description
The peek-function has many different and mostly unrelated uses. It is a kind
of grabbag for retrieving all kinds of numerical information, internal to
yabasic. The meaning of the numbers returned be the peek-function depends on
the string or number passed as an argument.
peek always returns a number, however the closely related peek$-function
exists, which may be used to retrieve string information from among the
internals of yabasic. Finally note, that some of the values which are
retrieved with peek may even be changed, using the poke-function.
There are two variants of the peek-function: One expects an integer,
positive number and is described within the first entry of the list below.
The other variant expects one of a well defined set of strings as described
in the second and all the following entries of the list below.
peek(a), peek(#a)
Read a single character from the file a (which must be open of
course).
peek("winheight")
Return the height of the graphic-window in pixels. If none is open,
this peek will return the height of the last window opened or 100, if
none has been opened yet.
peek("winwidth")
Return the width of the graphic-window in pixels. If none is open,
this peek will return the width of the last window opened or 100, if
none has been opened yet.
peek("fontheight")
Return the height of the font used within the graphic window. If none
is open, this peek will return the height of the last font used or
10, if no window has been opened yet.
peek("screenheight")
Return the height in characters of the window, wherein yabasic runs.
If you have not called clear screen yet, this peekwill return 0,
regardless of the size of your terminal.
peek("screenwidth")
Return the width in characters of the window, wherein yabasic runs.
If you have not called clear screen yet, this peekwill return 0,
regardless of the size of your terminal.
peek("argument")
Return the number of arguments, that have been passed to yabasic at
invocation time. E.g. if yabasic has been called like this: yabasic
foo.yab bar baz, then peek("argument") will return 2. This is because
foo.yab is treated as the name of the program to run, whereas bar and
baz are considered arguments to the program, which are passed on the
commandline. Note, that for windows-users, who tend to click on the
icon (as opposed to starting yabasic on the command line), this
peekwill mostly return 0.
The function peek("argument") can be written as peek("arguments")
too.
You will want to check out the corresponding function
peek$("argument") to actually retrieve the arguments. Note, that each
call to peek$("argument") reduces the number returned by
peek("argument").
peek("isbound")
Return true, if the executing yabasic-program is part of a standalone
program; see the section about creating a standalone-program for
details.
peek("version")
Return the version number of yabasic (e.g. 2.72).
peek("error")
Return a number specifying the nature of the last error in an open-
or seek-statement. Normally an error within an open-statement
immediately terminates your program with an appropriate
error-message, so there is no chance and no need to learn more about
the nature of the error. However, if you use open as a condition
(e.g. if (open(#1,"foo")) ...) the outcome (success or failure) of the
open-operation will determine, if the condition evaluates to true or
false. If now such an operation fails, your program will not be
terminated and you might want to learn the reason for failure. This
reason will be returned by peek("error") (as a number) or by
peek$("error") (as a string)
The table below shows the various error codes; the value returned by
peek$("error") explains the nature of the error. Note, that the codes
10,11 and 12 refer to the seek-command.
Table 6.1. Error codes
peek("error") peek$("error") Explanation
2 Stream already in use Do not try to open one and the same filenumber
twice; rather close it first.
3 'x' is not a valid filemode The optional filemode argument, which may be
passed to the open-function, has an invalid value
4 could not open 'foo' The open-call did not work, no further explanation is
available.
5 reached maximum number of open files You have opened more files than your
operating system permits.
6 cannot open printer: already printing graphics The commands open printer
and open #1,printer both open a printer (refer to their description for the
difference). However, only one can be active at a time; if you try to do
both at the same time, you will receive this error.
7 could not open line printer Well, it simply did not work.
9 invalid stream number An attempt to use an invalid (e.g. negative) stream
number; example: open(-1,"foo")
10 could not position stream x to byte y seek did not work.
11 stream x not open You have tried to seek within a stream, that has not
been opened yet.
12 seek mode 'x' is none of begin,end,here The argument, which has been
passed to seek is invalid.
Example
open "foo" for reading as #1
open "bar" for writing as #2
while(not eof(#1))
poke #2,chr$(peek(#1));
wend
This program will copy the file foo byte by byte to bar.
Note, that each peek does something entirely different, and only one has
been demonstrated above. Therefore you need to make up examples yourself for
all the other peeks.
See also
peek$, poke, open
peek$
Name
peek$ - retrieve various internal string-informations
Synopsis
print peek$("foo")
Description
The peek$-function has many different and unrelated uses. It is a kind of
grabbag for retrieving all kinds of string information, internal to yabasic;
the exact nature of the strings returned be the peek$-function depends on
the string passed as an argument.
peek$ always returns a string, however the closely related peek-function
exists, which may be used to retrieve numerical information from among the
internals of yabasic. Finally note, that some of the values which are
retrieved with peek$ may even be changed, using the poke-function.
The following list shows all possible arguments to peek$:
peek$("infolevel")
Returns either "debug", "note", "warning", "error" or "fatal",
depending on the current infolevel. This value can be specified with
an option (either under windows or unix) on the commandline or
changed during the execution of the program with the corresponding
poke; however, normally only the author of yabasic (me !) would want
to change this from its default value "warning".
peek$("textalign")
Returns one of nine possible strings, specifying the default
alignment of text within the graphics-window. The alignment-string
returned by this peek describes, how the text-command aligns its
string-argument with respect to the coordinates supplied. However,
this value does not apply, if the text-command explicitly specifies
an alignment. Each of these strings is two characters long. The first
character specifies the horizontal alignment and can be either l, r
or c, which stand for left, right or center. The second character
specifies the vertical alignment and can be one of t, b or c, which
stand for top, bottom or center respectively.
You may change this value with the corresponding command poke
"textalign",...; the initial value is lb, which means the top of the
left and the top edge if the text will be aligned with the
coordinates, that are specified within the text-command.
peek$("windoworigin")
This peek returns a two character string, which specifies the
position of the origin of the coordinate system of the window; this
string might be changed with the corresponding command poke
"windoworigin",x,y or specified as the argument of the origin
command; see there for a detailed description of the string, which
might be returned by this peek.
peek$("error")
Return a string describing the nature of the last error in an open-
or seek-statement. See the corresponding peek("error") for a detailed
description.
peek$("library")
Return the name of the library, this statement is contained in. See
the import-command for a detailed description or for more about
libraries.
peek$("os")
This peek returns the name of the operating system, where your
program executes. This can be either windows or unix.
peek$("font")
Return the name of the font, which is used for text within the
graphic window; this value can be specified as the third argument to
the open window-command.
peek$("env","NAME")
Return the environment variable specified by NAME (which may be any
string expression). Which kind of environment variables are available
on your system depends, as well as their meaning, on your system;
however typing env on the commandline will produce a list (for
Windows and Unix alike). Note, that peek$("env",...) can be written
as peek$("environment",...) too.
peek$("argument")
Return one of the arguments, that have been passed to yabasic at
invocation time (the next call will return the the second argument,
and so on). E.g. if yabasic has been called like this: yabasic
foo.yab bar baz, then the first call to peek$("argument") will return
bar. This is because foo.yab is treated as the name of the program to
run, whereas bar and baz are considered arguments to this program,
which are passed on the commandline. The second call to
peek$("argument") will return baz. Note, that for windows-users, who
tend to click on the icon (as opposed to starting yabasic on the
command line), this peekwill mostly return the empty string.
Note, that peek$("argument") can be written as peek$("arguments").
Finally you will want to check out the corresponding function
peek("argument").
Example
print "You have supplied these arguments: "
while(peek("argument"))
print peek("argument"),peek$("argument")
wend
If you save this program in a file foo.yab and execute it via yabasic t.yab
a b c (for windows users: please use the commandline for this), your will
get this output:
3a
2b
1c
See also
peek, poke, open
pi
Name
pi - a constant with the value 3.14159
Synopsis
print pi
Description
pi is 3.14159265359 (well at least for yabasic); do not try to assign to pi
(e.g. pi=22/7) this would not only be mathematically dubious, but would also
result in a syntax error.
Example
for a=0 to 180
print "The sine of ",a," degrees is ",sin(a*pi/180)
next a
This program uses pi to transform an angle from degrees into radians.
See also
euler
poke
Name
poke - change selected internals of yabasic
Synopsis
poke "foo","bar"
poke "foo",baz
poke #a,"bar"
poke #a,baz
Description
The poke-command may be used to change details of yabasics behaviour. Like
the related function peek, poke does many different things, depending on the
arguments supplied.
Here are the different things you can do with poke:
poke "textalign","cc"
This poke changes the default alignment of text with respect to the
coordinates supplied within the text-command. However, this value
does not apply, if the text-command explicitly specifies an
alignment. The second argument ("cc" in the example) must always be
two characters long; the first character can be one of l (left), r
(right) or c (center); the second character can be either t (top), b
(bottom) or c (center); see the corresponding peek$("textalign") for
a detailed description of this argument.
poke "windoworigin","lt"
This poke moves the origin of the coordinate system of the window to
the specified position. The second argument ("lt" in the example)
must always be two characters long; the first character can be one of
l (left), r (right) or c (center); the second character can be either
t (top), b (bottom) or c (center). Together those two characters
specify the new position of the coordinate-origin. See the
corresponding peek$("windoworigin") for a more in depth description
of this argument.
poke "infolevel","debug"
Change the amount of internal information, that yabasic outputs
during execution.
The second argument can be either "debug", "note", "warning", "error"
or "fatal". However, normally you will not want to change this from
its default value "warning".
See also the related peek$("infolevel").
poke #1,a
Write the given byte (a in the example above) to the specified stream
(#a in the example).
See also the related function function peek(#1).
Example
print "Hello, now you will see, how much work"
print "a simple for-loop involves ..."
input "Please press return " a$
poke "infolevel","debug"
for a=1 to 10:next a
This example only demonstrates one of the many pokes, which are described
above: The program switches the infolevel to debug, which makes yabasic
produce a lot of debug-messages during the subsequent for-loop.
See also
peek, peek$
print
Name
print - Write to terminal or file
Synopsis
print "foo",a$,b
print "foo","a$,b;
print #a "foo",a$
print #a "foo",a$;
print foo using "##.###"
print reverse "foo"
print at(10,10) a$,b
print @(10,10) a$,b
print color("red","blue") a$,b
print color("magenta") a$,b
print color("green","yellow") at(5,5) a$,b
Description
The print-statement outputs strings or characters, either to your terminal
(also known as console) or to an open file.
To understand all those uses of the print-statement, let's go throught the
various lines in the synopsis above:
print "foo",a$,b
Print the string foo as well as the contents of the variables a$ and
b onto the screen, silently adding a newline.
print "foo",a$,b;
(Note the trailing semicolon !) This statement does the same as the
one above; only the implicit newline is skipped, which means that the
next print-statement will append seamlessly.
print #a "foo",a$
This is the way to write to files. The file with the number a must be
open already, an implicit newline is added. Note the file-number #a,
which starts with a hash ('#') amd is separated from the rest of the
statement by a space only. The file-number (contained in the variable
a) must have been returned by a previous open-statement (e.g.
a=open("bar")).
print #a "foo",a$;
The same as above, but without the implicit newline.
print foo using "##.###"
Print the number foo with as many digits before and after the decimal
dot as given by the number of '#'-signs. See the entries for using
and str$ for a detailed description of this format.
print reverse "foo"
As all the print-variants to follow, this form of the print-statement
can only be issued after clear screen has been called. The strings
and numbers after the reverse-clause are simply printed inverse
(compared to the normal print-statement).
print at(10,10) a$,b
Print at the specified (x,y)-position. This is only allowed after
clear screen has been called. You may want to query
peek$("screenwidth") or peek$("screenheight") to learn the actual
size of your screen. You may add a semicolon to suppress the implicit
newline.
print @(10,10) a$,b
This is exactly the same as above, however, at may be written as @.
print color("red","blue") at(5,5) a$,b
Print with the specified fore- ("red") and background ("blue") color
(or colour). The possible values are "black", "white", "red", "blue",
"green", "yellow", "cyan" or "magenta". Again, you need to call clear
screen first and add a semicolon if you want to suppress the implicit
newline.
print color("magenta") a$,b
You may specify the foreground color only.
print color("green","yellow") a$,b
A color and a position (in this sequence, not the other way around)
may be specified at once.
Example
clear screen
columns=peek("screenwidth")
lines=peek("screenheight")
dim col$(7)
for a=0 to 7:read col$(a):next a
data "black","white","red","blue","green","yellow","cyan","magenta"
for a=0 to 2*pi step 0.1
print colour(col$(mod(i,8))) at(columns*(0.8*sin(a)+0.9)/2,lines*(0.8*cos(a)+
0.9)/2) "*"
i=i+1
next a
This example draws a cloured ellipse within the text window.
See also
at, print color, input, clear screen, using, ;
print color
Name
print color - print with color
Synopsis
print color(fore$) text$
print color(fore$,back$) text$
Description
Not a seperate command, but part of the print-command; may be included just
after print and can only be issued after clear screen has been executed.
color() takes one or two string-arguments, specifying the color of the text
and (optionally) the background.
The one or two strings passed to color() can be one of these: "black",
"white", "red", "blue", "green", "yellow", "cyan" and "magenta" (which can
be abbreviated as "bla", "whi", "red", "blu", "gre", "yel", "cya" and "mag"
respectively).
color() can only be used, if clear scren has been issued at least once.
Note, that color() can be written as colour() too.
Example
clear screen
dim col$(7):for a=0 to 7:read col$(a):next a
do
print color(col$(ran(7)),col$(ran(7))) " Hallo ";
pause 0.01
loop
data "black","white","red","blue"
data "green","yellow","cyan","magenta"
This prints the word " Hallo " in all colors accross your screen.
See also
print, clear screen, at
print colour
Name
print colour - see color
Synopsis
print colour(fore$) text$
print colour(fore$,back$) text$
See also
color
putbit
Name
putbit - draw a rectangle of pixels encoded within a string into the
graphics window
Synopsis
open window 200,200
a$=getbit(20,20,50,50)
putbit a$,30,30
putbit a$ to 30,30
putbit a$,30,30,"or"
Description
The putbit-command is the counterpart of the getbit-function. putbit
requires a string as returned by the getbit-function. Such a string contains
a rectangle from the graphic window; the putbit-function puts such a
rectangular region back into the graphic-window.
Note, that the putbit-command currently accepts a third argument. However
only the string value "or" is supported here. The effect is, that only those
pixel, which are set in the string will be set in the graphic window. Those
pixels, which are not set in the string, will not change in the window (as
opposed to beeing cleared).
Note, that the format of the string returned by this function is due to
change as soon as yabasic will learn, how to deal with colors.
Example
c$="rgb 21,21:0000000000000000000000000000000000000000000000000000000000000032c
8000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000032c80032c80032c80032c80032c80032c80032c80032c80032c80000000
000000000000000000000000000000000000000000000000000000032c80032c80032c80032c800
32c80032c80032c80032c80032c80032c80032c80032c8000000000000000000000000000000000
0000000000000000032c80032c80032c80032c80032c80032c80032c80032c80032c80032c80032
c80032c80032c80032c80032c80000000000000000000000000000000032c80032c80032c80032c
80032c80032c80032c80032c8c8ff000032c80032c80032c80032c80032c80032c80032c8000000
0000000000000000000000000032c80032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c
8ff00c8ff00c8ff000032c80032c80032c80032c80032c80000000000000000000032c80032c800
32c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c8003
2c80032c80032c80032c80000000000000032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff
00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c80032c80032c800000000000
00032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00
c8ff00c8ff000032c80032c80032c80032c80000000000000032c80032c80032c80032c8c8ff00c
8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c80032c800
32c80000000032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8f
f00c8ff00c8ff00c8ff00c8ff000032c80032c80032c80032c80000000000000032c80032c80032
c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c
80032c80032c80032c80000000000000032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00
c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c80032c80032c80000000000000
032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8
ff00c8ff000032c80032c80032c80032c80000000000000032c80032c80032c80032c80032c8c8f
f00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff00c8ff000032c80032c80032c80032c80032
c80000000000000000000032c80032c80032c80032c80032c8c8ff00c8ff00c8ff00c8ff00c8ff0
0c8ff00c8ff000032c80032c80032c80032c80032c80000000000000000000000000032c80032c8
0032c80032c80032c80032c80032c80032c80032c80032c80032c80032c80032c80032c80032c80
032c80000000000000000000000000000000000000032c80032c80032c80032c80032c80032c800
32c80032c80032c80032c80032c80032c80032c80032c80032c8000000000000000000000000000
0000000000000000032c80032c80032c80032c80032c80032c80032c80032c80032c80032c80032
c80032c80000000000000000000000000000000000000000000000000000000000000000000032c
80032c80032c80032c80032c80032c80032c80032c80032c8000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000"
open window 200,200
do
x=ran(220)-10
y=ran(220)-10
putbit c$,x,y,"transparent"
loop
This program uses a precanned string (containing the image of a blue circle
with a yellow centre) and draws it repeatedly into the graphic-window. The
mode "transparent" ensures, that no pixels will be cleared.
There are two possible values for the third argument of putbit. Both modes
differ in the way, they replace (or not) any pixels from the window with
pixels from the bitmap having the background colour.
transparent or t
With this mode the pixels from the window will be kept, if the bitmap
contains pixels with background colour at this position; i.e. the
bitmap is transparent
solid or s
With this mode the pixels from the window will be overpainted with
the pixels from the bitmap in any case; i.e. the bitmap is solid
If you omit this argument, the default transparent applies.
See also
getbit$, open window
putscreen
Name
putscreen - draw a rectangle of characters into the text terminal
Synopsis
clear screen
a$=getscreen$(5,5,10,10)
putscreen a$,7,7
Description
The putscreen-command is the counterpart of the getscreen$-function.
putscreen requires a string as returned by the getscreen-function. Such a
string contains a rectangular detail from the terminal; the
putscreen-function puts such a region back into the terminal-window.
Note, that clear screen must have been called before.
Example
clear screen
for a=1 to 200
print color("red") "Hallo !";
print color("blue") "Welt !";
next a
r$=getscreen$(0,0,20,20)
for x=0 to 60
putscreen r$,x,0
sleep 0.1
next x
This example prints the string "Hallo !Welt !" all over the screen and then
moves a rectangle from one side to the other.
See also
getscreen$, clear screen
R
Table of Contents
ran() - return a random number
read - read data from data-statements
rectangle - draw a rectangle
redim - create an array prior to its first use. A synonym for dim
rem - start a comment
repeat - start a repeat-loop
restore - reposition the data-pointer
return - return from a subroutine or a gosub
reverse - print reverse (background and foreground colors exchanged)
right$() - return (or change) the right end of a string
rinstr() - find the rightmost occurence of one string within the other
rtrim$() - trim spaces at the right end of a string
ran()
Name
ran() - return a random number
Synopsis
print ran()
x=ran(y)
Description
The ran-function returns a random number. If no argument is given, the
number returned is in the range from 0 to 1; where only 0 is a possible
value; 1 will never be returned. If an argument is supplied, the number
returned will be in the range from 0 up to this argument, whereas this
argument itself is not a possible return value.
Example
clear screen
c=peek("screenwidth")-1
l=peek("screenheight")
dim col$(8)
for a=0 to 7:read col$(a):next a
data "black","white","red","blue","green","yellow","cyan","magenta"
do
x=ran(c)
y=l-ran(l*exp(-32*((x/c-1/2)**2)))
i=i+1
print color(col$(mod(i,8))) at(x,y) "*";
loop
This example will print a cloured bell-curve.
See also
int
read
Name
read - read data from data-statements
Synopsis
read a$,a
data "Hello !",7
Description
The read-statement retrieves literal data, which is stored within
data-statements elsewhere in your program.
Example
read num
dim col$(num)
for a=1 to num:read col$(a):next a
clear screen
print "These are the colours known to yabasic:\n"
for a=1 to num
print colour(col$(a)) col$(a)
next a
data 8,"black","white","red","blue"
data "green","yellow","cyan","magenta"
This program prints the names of the colors known to yabasic in those very
colors.
See also
data, restore
rectangle
Name
rectangle - draw a rectangle
Synopsis
open window 100,100
rectangle 10,10 to 90,90
rectangle 20,20,80,80
rect 20,20,80,80
box 30,30,70,70
clear rectangle 30,30,70,70
fill rectangle 40,40,60,60
clear fill rectangle 60,60,40,40
Description
The rectangle-command (also known as box or rect, for short) draws a
recatangle; it accepts four parameters: The x- and y-coordinates of two
facing cornerpoints of the rectangle. With the optional clauses clear and
fill (which may appear both and in any sequence) the rectangle can be
cleared and filled respectively.
Example
open window 200,200
c=1
do
for phi=0 to pi step 0.1
if (c) then
rectangle 100+100*sin(phi),100+100*cos(phi) to 100-100*sin(phi),100-100*c
os(phi)
else
clear rectangle 100+100*sin(phi),100+100*cos(phi) to 100-100*sin(phi),100
-100*cos(phi)
endif
sleep 0.1
next phi
c=not c
loop
This example draws a nice animated pattern; watch it for a couple of hours,
to see how it develops.
See also
open window, open printer, line, circle, triangle
redim
Name
redim - create an array prior to its first use. A synonym for dim
Synopsis
See the dim-command.
Description
The redim-command does exactly the same as the dim-command; it is just a
synonym. redim has been around in older versions of basic (not even yabasic)
for many years; therefore it is supported in yabasic for compatibility
reasons.
Please refer to the entry for the dim-command for further information.
rem
Name
rem - start a comment
Synopsis
rem Hey, this is a comment
# this is a comment too
// even this
print "Not a comment" # This is an error !!
print "Not a comment":// But this is again a valid comment
print "Not a comment" // even this.
print "Not a comment" rem and this !
Description
rem introduces a comment (like # or //), that extends up to the end of the
line.
Those comments do not even need a colon (':' infront of them); they (rem, #
and //) all behave alike except for #, which may only appear at the very
beginning of a line; therefore the fourth example in the synopsis above
(print "Not a comment" # This is an error !!) is indeed an error.
Note, that rem is an abbreviation for remark. remark however is not a valid
command in yabasic.
Finally note, that a comment intoduced with '#' may have a special meaning
under unix; see the entry for # for details.
Example
#
rem comments on data structures
# are more useful than
// comments on algorithms.
rem
This program does nothing, but in a splendid and well commented way.
See also
#, //
repeat
Name
repeat - start a repeat-loop
Synopsis
repeat
...
until (...)
Description
The repeat-loop executes all the statements up to the final until-keyword
over and over. The loop is executed as long as the condition, which is
specified with the until-clause, becomes true. By construction, the
statements within the loop are executed at least once.
Example
x=0
clear screen
print "This program will print the numbers from 1 to 10"
repeat
x=x+1
print x
print "Press any key for the next number, or 'q' to quit"
if (inkey$="q") break
until(x=10)
This program is pretty much useless, but self-explanatory.
See also
until, break, while, do
restore
Name
restore - reposition the data-pointer
Synopsis
read a,b,c,d,e,f
restore
read g,h,i
restore foo
data 1,2,3
label foo
data 4,5,6
Description
The restore-command may be used to reset the reading of data-statements, so
that the next read-statement will read data from the first data-statement.
You may specify a label with the restore-command; in that case, the next
read-statement will read data starting at the given label. If the label is
omitted, reading data will begin with the first data-statement within your
program.
Example
input "Which language (german/english) ? " l$
if (instr("german",l$)>0) then
restore german
else
restore english
endif
for a=1 to 3
read x,x$
print x,"=",x$
next a
label english
data 1,"one",2,"two",3,"three"
label german
data 1,"eins",2,"zwei",3,"drei"
This program asks to select one of those languages known to me (i.e. english
or german) and then prints the numbers 1,2 and 3 and their textual
equivalents in the chosen language.
See also
read, data, label
return
Name
return - return from a subroutine or a gosub
Synopsis
gosub foo
label foo
return
sub bar(baz)
...
return quertz
end sub
Description
The return-statement serves two different (albeit somewhat related)
purposes. The probably more important use of return is to return control
from within a subroutine to the place in your program, where the subroutine
has been called. If the subroutine is declared to return a value, the
return-statement might be accompanied by a string or number, which
constitutes the return value of the subroutine.
However, even if the subroutine should return a value, the return-statement
need not carry a value; in that case the subroutine will return 0 or the
empty string (depending on the type of the subroutine). Moreover, feel free
to place multiple return-statements within your subroutine; it's a nice way
of controlling the flow of execution.
The second (but historcially first) use of return is to return to the
position, where a prior gosub has left off. In that case return may not
carry a value.
Example
do
read a$
if (a$="") then
print
end
endif
print mark$(a$)," ";
loop
data "The","quick","brown","fox","jumped"
data "over","the","lazy","dog",""
sub mark$(a$)
if (instr(lower$(a$),"q")) return upper$(a$)
return a$
end sub
This example features a subroutine mark$, that returns its argument in upper
case, if it contains the letter "q", or unchanged otherwise. In the
test-text the word quick will end up beeing marked as QUICK.
The example above demonstrates return within subroutines; please see gosub
for an example of how to use return in this context.
See also
sub, gosub
reverse
Name
reverse - print reverse (background and foreground colors exchanged)
Synopsis
clear screen
print reverse "foo"
Description
reverse may be used to print text in reverse. reverse is not a seperate
command, but part of the print-command; it may be included just after the
print and can only be issued once that clear screen has been issued.
Example
clear screen
print "1 ";
c=3
do
prim=true
for a=2 to sqrt(c)
if (frac(c/a)=0) then
prim=false
break
endif
next a
if (prim) then
print
print reverse c;
else
print c;
endif
print " ";
c=c+1
loop
This program prints numbers from 1 on and marks each prime number in
reverse.
See also
at, print color, print, clear screen
right$()
Name
right$() - return (or change) the right end of a string
Synopsis
print right$(a$,2)
right$(b$,2)="baz"
Description
The right$-function requires two arguments (a string and a number) and
returns the part from the right end of the string, whose length is specified
by its second argument. So, right$ simply returns the requested number of
chars from the right end of the given string.
Note, that the right$-function can be assigned to, i.e. it may appear on the
left hand side of an assignment. In this way it is possible to change a part
of the variable used within the right$-function. Note, that that way the
length of the string cannot be changed, i.e. characters might be
overwritten, but not added. For an example see below.
Example
print "Please enter a length either in inch or centimeter"
print "please add 'in' or 'cm' to mark the unit."
input "Length: " a$
if (right$(a$,2)="in") then
length=val(a$)*2.56
elsif (right$(a$,2)="cm") then
length=val(a$)
else
error "Invalid input: "+a$
endif
This program allows the user to enter a length qulified with a unit (either
inch or centimeter).
This second example demonstrates the capability to assign to the
right$-function.
a$="Heiho World !"
print a$
right$(a$,7)="dwarfs."
print a$
See also
right$ and mid$
rinstr()
Name
rinstr() - find the rightmost occurence of one string within the other
Synopsis
pos=rinstr("Thequickbrownfox","equi")
pos=rinstr(a$,b$,x)
Description
The rinstr-function accepts two string-arguments and tries to find the
second within the first. However, unlike the instr, the rinstr-function
finds the rightmost (or last) occurence of the string; whereas the
instr-function finds the leftmost (or first) occurence. In any case however,
the position is counted from the left.
If you supply a third, numeric argument to the rinstr-function, it will be
used as a starting point for the search. Therefore
rinstr("abcdeabcdeabcde","e",8) will return 5, because the search for an "e"
starts at position 8 and finds the first one at position 5.
Example
print rinstr("foofoofoobar","foo")
This simple example will print 7, because it finds the rightmost among the
three occurences of foo within the string. Note, that
print instr("foofoofoobar","foo")
would have printed 1.
See also
instr
rtrim$()
Name
rtrim$() - trim spaces at the right end of a string
Synopsis
a$=rtrim$(b$)
Description
The rtrim$-function removes all wthitespace from the right end of a string
and returns the result.
Example
open 1,"foo"
dim lines$(100)
l=1
while(not eof(1))
input #1 a$
a$=rtrim$(a$)
if (right$(line$,1)="\\") then
line$=line$+" "+a$
else
lines$(l)=line$
l=l+1
line$=a$
endif
end while
print "Read ",l," lines"
This example reads the file foo allowing for continuation lines, which are
marked by a \, which appears as the last character on a line. For
convenience whitespace at the right end of a line is trimmed with rtrim.
See also
ltrim$, trim$
S
Table of Contents
screen - as clear screen clears the text window
seek() - change the position within an open file
sig() - return the sign of its argument
sin() - return the sine of its single argument
sleep - pause, sleep, wait for the specified number of seconds
split() - split a string into many strings
sqr() - compute the square of its argument
sqrt() - compute the square root of its argument
static - preserves the value of a variable between calls to a subroutine
step - specifies the increment step in a for-loop
str$() - convert a number into a string
sub - declare a user defined subroutine
switch - select one of many alternatives depending on a value
system$() - hand a statement over to your operating system and return its
output
system() - hand a statement over to your operating system and return its
exitcode
screen
Name
screen - as clear screen clears the text window
Synopsis
clear screen
Description
The keyword screen appears only within the sequence clear screen; please see
there for a description.
See also
clear screen
seek()
Name
seek() - change the position within an open file
Synopsis
open 1,"foo"
seek #1,q
seek #1,x,"begin"
seek #1,y,"end"
seek #1,z,"here"
Description
The seek-command changes the position, where the next input (or peek)
statement will read from an open file. Usually files are read from the
beginning to the end sequentially; however sometimes you may want to depart
from this simple scheme. This can be done with the seek-command, allowing
you to change the position, where the next piece of data will be read from
the file.
seek accepts two or three arguments: The first one is the number of an
already open file. The second one is the position where the next read from
the file will start. The third argument is optional and specifies the the
point from where the position (the second argument) will count. It can be
one of:
begin
Count from the beginning of the file.
end
Count from the end of the file.
here
Count from the current position within the file.
Example
open #1,"count.dat","w"
for a=1 to 10
print #1,"00000000";
if (a<10) print #1,";";
next a
dim count(10)
do
x=int(ran(10))
i=i+1
if (mod(i,1000)=0) print ".";
count(x)=count(x)+1
curr$=right$("00000000"+str$(count(x)),8)
seek #1,9*x,"begin"
print #1,curr$;
loop
This example increments randomly one of ten counters (in the array count());
however, the result is always kept and updated within the file count.dat, so
even in case of an unexpected interrupt, the result will not be lost.
See also
tell, open, print, peek
sig()
Name
sig() - return the sign of its argument
Synopsis
a=sig(b)
Description
Return +1, -1 or 0, if the single argument is positive, negative or zero.
Example
clear screen
dim c$(3):c$(1)="red":c$(2)="white":c$(3)="green"
do
num=ran(100)-50
print color(c$(2+sig(num))) num
loop
This program prints an infinite sequence of random number; positive numbers
are printed in green, negative numbers are printed red (an exact zero would
be printed white). (With a little extra work, this program could be easily
extended into a brogerage system)
See also
abs, int, frac
sin()
Name
sin() - return the sine of its single argument
Synopsis
y=sin(angle)
Description
The sin-function expects an angle (in radian, not degree) and returns its
sine.
Example
open window 200,200
new curve
for phi=0 to 2*pi step 0.1
line to 100+90*sin(phi),100+90*cos(phi)
next phi
close curve
This program draws a circle (ignoring the existence of the circle-command).
See also
asin, cos
sleep
Name
sleep - pause, sleep, wait for the specified number of seconds
Synopsis
sleep 4
Description
The sleep-command has many different names: You may write pause, sleep or
wait interchangable; whatever you write, yabasic will always do exactly the
same.
Therefore you should refer to the entry for the pause-function for further
information.
split()
Name
split() - split a string into many strings
Synopsis
dim w$(10)
num=split(a$,w$())
num=split(a$,w$(),s$)
Description
The split-function requires a string (containing the text to be split), a
reference to a string-array (which will receive the resulting strings, i.e.
the tokens) and an optional string (with a set of characters, at which to
split, i.e. the delimiters).
The split-function regards its first argument (a string) as a list of tokens
separated by delimiters and it will store the list of tokens within the
array-reference you have supplied. Note, that the array, which is passed as
a reference (w$() in the synopsis), will be resized accordingly, so that you
don't have to figure out the number of tokens in advance. The element at
position zero (i.e. w$(0)) will not be used.
normally (i.e. if you omit the third, which is the delimiter-argument) the
function will regard space or tab as delimiters for tokens; however by
supplying a third argument, you may split at any single of the characters
within this string. E.g. if you supply ":;" as the third argument, then
colon (:) or semicolon (;) will delimit tokens.
Note, that a sequence of separator-characters will produce a sequence of
empty tokens; that way, the number of tokens returned will always be one
plus the number of separator characters contained within the string. Refer
to the closely related token-function, if you do not like this behaviour. In
some way, the split-function focuses on the separators (other than the
token-function, which focuses on the tokens), hence its name.
The second argument is a reference on a string-array, where the tokens will
be stored; this array will be expanded (or shrinked) to have room for all
tokens, if necessary.
The first argument finally contains the text, that will be split into
tokens. The split-function returns the number of tokens that have been
found.
Please see the examples below for some hints on the exact behaviour of the
split-function and how it differs from the token-function:
Example
print "This program will help you to understand, how the"
print "split()-function exactly works and how it behaves"
print "in certain special cases."
print
print "Please enter a line containing tokens separated"
print "by either '=' or '-'"
dim t$(10)
do
print
input "Please enter a line: " l$
num=split(l$,t$(),"=-")
print num," Tokens: ";
for a=1 to num
if (t$(a)="") then
print "(EMPTY)";
else
print t$(a);
endif
if (a<num) print ",";
next a
print
loop
This program prints the following output:
Please enter a line: a
1 Tokens: a
Please enter a line:
0 Tokens:
Please enter a line: ab
1 Tokens: ab
Please enter a line: a=b
2 Tokens: a,b
Please enter a line: a-
2 Tokens: a,(EMPTY)
Please enter a line: a-=
3 Tokens: a,(EMPTY),(EMPTY)
Please enter a line: =a-
3 Tokens: (EMPTY),a,(EMPTY)
Please enter a line: a=-b
3 Tokens: a,(EMPTY),b
Please enter a line: a--b-
4 Tokens: a,(EMPTY),b,(EMPTY)
Please enter a line: -a==b-c==
7 Tokens: (EMPTY),a,(EMPTY),b,c,(EMPTY),(EMPTY)
See also
token
sqr()
Name
sqr() - compute the square of its argument
Synopsis
a=sqr(b)
Description
The sqr-function computes the square of its numerical argument (i.e. it
multiplies its argument with itself).
Example
for a=1 to 10
print a,sqr(a),a**2
next a
As you may see from the output, sqr can be written as **2 (or ^2) too.
See also
sqrt, **, ^
sqrt()
Name
sqrt() - compute the square root of its argument
Synopsis
to be written
Description
The sqrt-function computes the square root of its numerical argument.
Example
for a=1 to 5
print a,sqrt(a),a**(1/2)
next a
As you may see from the output, sqrt can be written as **(1/2) (or ^(1/2))
too.
See also
sqr, **, ^
static
Name
static - preserves the value of a variable between calls to a subroutine
Synopsis
sub foo()
static a
...
end sub
Description
The static keyword can be used within subroutines to mark variables as
static. This has two effects: First, the variable is local to the
subroutine, i.e. its value is not know outside the subroutine (this is the
effect of the local keyword). Second, the static-keyword arranges things, so
that the variable keeps its value between invocations of the subroutine
(this is different from the local-keyword).
Example
foo()foo()foo()
sub foo()
static a
local b
a=a+1
b=b+1
print a,b
end sub
This program shows the difference between static and local variables within
a subroutine; it produces this output:
1 1
2 1
3 1
The output shows, that the static variable a keeps its value between
subroutine calls, whereas b is initialized with the value 0 at every call to
the subroutine foo.
See also
sub, local
step
Name
step - specifies the increment step in a for-loop
Synopsis
for a=1 to 10 step 3
...
next a
Description
Specify, by which amount the loop-variable of a for-loop will be incremented
at each step.
The step (as well as the lower and upper bound) are computed anew in each
step; this is not common, but possible, as the example below demonstrates.
Example
for x=1 to 1000 step y
y=x+y
print x," ",y," ";
next x
print
This program computes the fibonacci numbers between 1 and 1000.
See also
for
str$()
Name
str$() - convert a number into a string
Synopsis
a$=str$(a)
b$=str$(x,"##.###")
b$=str$(x,"###,###.##")
b$=str$(x,"###,###.##","_.")
Description
The str$-function accepts a numeric argument and returns it as a string.
This conversion between number and string can be controlled with the
optional third argument (the format argument). See the following table of
examples to learn about valid values of this argument. Note, that those
examples fall in one of two categories: C-style and basic-style; the first 4
examples in the table below are C-style, the rest of the examples are
basic-style. For more information on the C-style formats, you may refer to
your favorite documentation on the C programming language. The basic-style
formats are much simpler, they just depict the desired output, marking
digits with '#'; groups of (usually three) digits may be separated with
colons (','), the decimal dot must be marked by a literal dot ('.').
Moreover these characters (colons and dot) may be replaced by other
characters to satisfy the needs of non-english (e.g. german) languages; see
the examples below.
Note, that for clarity, each space in the result has been replaced by the
letter 'x', because it would be hard to figure out, how many spaces are
produced exactly otherwise.
Table 6.2. Examples for the format argument
Example string Result for converting 1000*pi Description
%2.5f 3141.59265 The '2' determines the minimum length of the output; but if
needed (as in the example) the output can be longer. The '5' is the number
of digits after the decimal point.
%12.5f xx3141.59265 Two spaces (which appear as 'x') are added to pad the
output to the requested length of 12 characters.
%012.5g 0000003141.6 The 'g' requests, that the precision ('5') specifies
the overall number of digits (before and after the decimal point).
%-12.5f 3141.59265xx The '-' requests the output to be left-centered
(therefor the filling space appears at thi right).
#####.## x3141.59 Each '#' specifies a digit (either before or after the
dot), the '.' specifies the position of the dot. As 1000*pi does not have
enough digits, the 5 requested digits before the dot are filled up with a
space (which shows up as an 'x').
##,###.## x3,141.59 Nearly the same as above, but the colon from the format
shows up within the result.
##,###.## and an addtional argument of ".," x3.141,59 Similar to the example
above, but colon and dot are replaced with dot and colon respectivly.
##,###.## and an addtional argument of "_," x3_141,59 Similar to the example
above, but colon and dot are replaced with underscore and colon respectivly.
##### x3142 The format string does not contain a dot, and therefore the
result does not have any fractional digits.
##.### ##.### As 1000*pi has 4 digits infront of the decimal dot and the
format only specifies 2, yabasic does not know what to do; therefore it
chooses just to reproduce the format string.
Example
do
input "Please enter a format string: " f$
a$=str$(1000*pi,f$)
for a=1 to len(a$)
if (mid$(a$,a,1)=" ") mid$(a$,a,1)="x"
next a
print a$
loop
This is the program, that has been used to get the results shown in the
table above.
See also
print, using
sub
Name
sub - declare a user defined subroutine
Synopsis
foo(2,"hello")
sub foo(bar,baz$)
...
return qux
...
end sub
Description
The sub-keyword starts the definition of a user defined subroutine. With
user defined subroutines you are able to somewhat extend yabasic with your
own commands or functions. A subroutine accepts arguments (numbers or
strings) and returns a number or a string (however, you are not required to
assign the value returned to a variable).
The name of the subroutine follows after the keyword sub. If the name (in
the synopsis: foo) ends on a '$', the subroutine should return a string
(with the return-statement), otherwise a number.
After the name of the subroutine yabasic requires a pair of braces; within
those braces you may specify a list of parameters, for which values can (but
need not) be included when calling the subroutine. If you omit one of those
parameters when calling such a subroutine, it assumes the value zero (for
numeric parameters) or the empty string (for string-parameters). However
with peek("argument") you may find out, how many arguments have really been
passed while calling the subroutine.
Parameters of a subroutine are always local variables (see the keyword local
for more explanation).
From within the subroutine you may return any time with the keyword return;
along with the return-keyword you may specify the return value. Note that
more than one return is allowed within a single subroutine.
Finally, the keyword end sub ends the subroutine definition. Note, that the
definition of a subroutine need not appear within the program before the
first call to this sub.
Note
As braces have two uses in yabasic (i.e. for supplying arguments to a
subroutine as well as to list the indices of an array). yabasic can not tell
apart an array from a subroutine with the same name. Therefore you cannot
define a subroutine with the same name as an array !
Example
p=2
do
if (is_prime(p)) print p
p=p+1
loop
sub is_prime(a)
local b
for b=2 to sqrt(a)
if (frac(a/b)=0) return false
next b
return true
end sub
This example is not the recommended way to compute prime numbers. However it
gives a nice demonstration of using a subroutine.
See also
local, static, peek
switch
Name
switch - select one of many alternatives depending on a value
Synopsis
switch a
case 1
case 2
...
end switch
switch a$
case "a"
case "b"
end switch
Description
The switch-statment selects one of many codepaths depending on a numerical
or string expression. I.e. it takes an expression (either numeric or string)
and compares it with a series of values, each wrapped within a case-clause.
If the expression equals the value given in a case-clause, the subsequent
statements are executed.
The default-clause allows to specify commands, which should be executed, if
none of case-clauses matches.
Note, that many case-clauses might be clustered (e.g. case "a":case "b":case
"c"). Or put another way: You need a break-statement at the end of a
case-branch, if you do not want to run into the next case.
Example
input "Please enter a single digit: " n
switch n
case 0:print "zero":break
case 1:print "one":break
case 2:print "two":break
case 3:print "three":break
case 4:print "four":break
case 5:case 6: case 7:case 8:case 9
print "Much !":break
default:print "Hey ! That was more than a single digit !"
end switch
This example translates a single digit into a string; note, how the cases 5
to 7 are clustered.
See also
switch, case, break
system$()
Name
system$() - hand a statement over to your operating system and return its
output
Synopsis
print system$("dir")
Description
The system$-command accepts a single string argument, specifying a command,
that can be found and executed by your operating system. It returns the
output of this command as one big string.
Example
input "Please enter the name of a directory: " d$
print
print "This is the contents of the '"+d$+"':"
print system$("dir "+d$)
This example lists the contents of a directory, employing the dir-command
(which is about the only program, that is known under Unix as well as
Windows).
See also
system
system()
Name
system() - hand a statement over to your operating system and return its
exitcode
Synopsis
ret=system("foo")
system("bar")
Description
The system-command accepts a single string argument, which specifies a
command to be executed. The function will return the exitcode of the
command; its output (if any) will be lost.
Example
print "Please enter the name of the file, that should be deleted."
input f$
if (system("rm "+f$+" >/dev/null 2>&1")) then
print "Error !"
else
print "okay."
endif
This program is Unix-specific: It uses the Unix-command rm to remove a file.
See also
system$
T
Table of Contents
tan() - return the tangens of its argument
tell - get the current position within an open file
text - write text into your graphic-window
then - tell the long from the short form of the if-statement
time$ - return a string containing the current time
to - this keyword appears as part of other statements
token() - split a string into multiple strings
triangle - draw a triangle
trim$() - remove leading and trailing spaces from its argument
true - a constant with the value of 1
tan()
Name
tan() - return the tangens of its argument
Synopsis
foo=tan(bar)
Description
The tan-function computes the tangens of its arguments (which should be
specified in radian).
Example
for a=0 to 45
print tan(a*pi/180)
next a
This example simply prints the tangens of all angles between 0 and 45
degree.
See also
atan, sin
tell
Name
tell - get the current position within an open file
Synopsis
open #1,"foo"
...
position=tell(#1)
Description
The tell-function requires the number of an open file as an argument. It
returns the position (counted in bytes, starting from the beginning of the
file) where the next read will start.
Example
open #1,"foo","w"
print #1 "Hello World !"
close #1
open #1,"foo"
seek #1,0,"end"
print tell(#1)
close 1
This example (mis)uses tell to get the size of the file. The seek positions
the file pointer at the end of the file, therefor the call to tell returns
the total length of the file.
See also
tell, open
text
Name
text - write text into your graphic-window
Synopsis
text x,y,"foo"
text x,y,"foo","lb"
text x,y,"foo","cc","font"
text x,y,"foo","font","rt"
Description
The text-commands displays a text-string (the third argument) at the given
position (the first two arguments) within an already opened window. The font
to be used can be optionally specified as either the fourth or fifth
argument ("font" in the example above). A font specified this way will also
be used for any subsequent text-commands, as long as they do not specify a
font themselves.
The fourth or fifth optional argument ("lb" in the example above) can be
used to specify the alignment of the text with respect to the specified
position. This argument is always two characters long: The first character
specifies the horizontal alignment and can be either l, r or c, which stand
for left, right or center. The second character specifies the vertical
alignment and can be one of t, b or c, which stand for top, bottom or center
respectively. If you omit this alignment argument, the default "lb" applies;
however this default may be changed with poke "textalign","xx"
Example
open window 500,200
clear screen
data "lt","lc","lb","ct","cc","cb","rt","rc","rb"
for a=1 to 9
read align$
print "Alignment: ",align$
line 50*a-15,100,50*a+15,100
line 50*a,85,50*a,115
text 50*a,100,"Test",align$
inkey$
next a
This program draws nine crosses and writes the same text at each; however it
goes through all possible nine alignment strings, showing their effect.
See also
open window, peek, poke
then
Name
then - tell the long from the short form of the if-statement
Synopsis
if (a<b) then
...
endif
Description
The keyword then is part of the if-statement; please see there for further
explanations. However, not every if-statement requires the keyword then: If
the keyword then is present, the if-clause may extend over more than one
line, and the keyword endif is required to end it. If the keyword then is
not present, the if-statement extends up to the end of the line, and any
endif would be an error.
Example
if (1<2) then
print "Hello ";
endif
if (2<3) print "world"
if (2<1)
print "!"
This example prints Hello world. Note, that no exclamation mark (!) is
printed, which might come as a surprise and may be changed in future
versions of yabasic.
See also
if
time$
Name
time$ - return a string containing the current time
Synopsis
print time$
print time$()
Description
The time$ function returns the current time in four fields separated by
hyphens '-'. The fields are:
* The current hour in the range from 0 to 23, padded with zeroes (e.g. 00
or 04) to a length of two characters.
* The number of minutes, padded with zeroes.
* The number of seconds, padded with zeroes.
* The number of seconds, that have elapsed since the program has been
started. This value encreases as long as your program runs and is
therefore unbound and not padded with zeroes.
At the time of writing this documentation, time$ returns 22-58-53-0. Note,
that the first three of the four fields returned by time$ have a fixed
width; therefore it is easy to extract some fields with the usual
string-functions mid$ (and others).
Example
print "Hello it is ",time$
print "An empty for-loop with ten million iterations takes ";
s=val(mid$(time$,10))
for a=1 to 10000000:next a
e=val(mid$(time$,10))
print e-s," seconds"
This program benchmarks the for-loop and uses the fourth field of the string
returned by time$.
See also
date
to
Name
to - this keyword appears as part of other statements
Synopsis
for a=1 to 100 step 2
...
next a
line x,y to a,b
Description
The to-keyword serves two purposes (which are not related at all):
* within for-statements, to specify the upper bound of the loop.
* Within any graphical command (e.g. line), that requires two points (i.e.
four numbers) as arguments, a comma ',' might be replaced with the
keyword to. I.e. instead of 100,100,200,200 you may write 100,100 to
200,200 in such commands.
Example
Please see the command listed under "See also" for examples.
See also
for, line, rectangle
token()
Name
token() - split a string into multiple strings
Synopsis
dim w$(10)
num=token(a$,w$())
num=token(a$,w$(),s$)
Description
The token-function accepts a string (containing the text to be split), a
reference to a string-array (which will receive the resulting strings, i.e.
the tokens) and an optional string (with a set of characters, at which to
split, i.e. the delimiters).
The token-function regards its first argument as a list of tokens separated
by delimiters and it will store the list of tokens within the
array-reference that has been supplied. Note, that the array, which is
passed as a reference (w$() in the synopsis), will be resized accordingly,
so that you don't have to figure out the number of tokens in advance. The
element at position zero (i.e. w$(0)) will not be used.
Normally (i.e. if you omit the third, the delimiter-argument) the function
will regard space or tab as delimiters for tokens; however by supplying a
third argument, you may split at any single of the characters within this
string. E.g. if you supply ":;" as the third argument, then colon (:) or
semicolon (;) will delimit tokens.
Note, that token will never produce empty tokens, even if two or more
separators follow in sequence. Refer to the closely related split-function,
if you do not like this behaviour. In some way, the token-function focuses
on the tokens and not on the separators (other than the split-function,
which focuses on the separators).
The second argument is a reference on a string-array, where the tokens will
be stored; this array will be expanded (or shrinked) as necessary to have
room for all tokens.
The first argument finally contains the text, that will be split into
tokens. The token-function returns the number of tokens, that have been
found.
Please see the examples below for some hints on the exact behaviour of the
token-function and how it differs from the split-function:
Example
print "This program will help you to understand, how the"
print "token()-function exactly works and how it behaves"
print "in certain special cases."
print
print "Please enter a line containing tokens separated"
print "by either '=' or '-'"
dim t$(10)
do
print
input "Please enter a line: " l$
num=token(l$,t$(),"=-")
print num," Tokens: ";
for a=1 to num
if (t$(a)="") then
print "(EMPTY)";
else
print t$(a);
endif
if (a<num) print ",";
next a
print
loop
This program prints the following output:
Please enter a line: a
1 Tokens: a
Please enter a line:
0 Tokens:
Please enter a line: ab
1 Tokens: ab
Please enter a line: a=b
2 Tokens: a,b
Please enter a line: a-
1 Tokens: a
Please enter a line: a-=
1 Tokens: a
Please enter a line: =a-
1 Tokens: a
Please enter a line: a=-b
2 Tokens: a,b
Please enter a line: a--b-
2 Tokens: a,b
Please enter a line: -a==b-c==
3 Tokens: a,b,c
See also
split
triangle
Name
triangle - draw a triangle
Synopsis
open window 100,100
triangle 100,100,50,50,100,50
fill triangle 50,100,100,50,200,200
clear fill triangle 20,20,10,10,200,200
Description
The triangle-command draws a triangle; it requires 6 parameters: The x- and
y-coordinates of the three points making up the triangle. With the optional
keywords clear and fill (which may appear both and in any sequence) the
triangle can be cleared and filled respectively.
Example
open window 200,200
do
phi=phi+0.2
i=i+2
color mod(i,255),mod(85+2*i,255),mod(170+3*i,255)
dx=100*sin(phi):dy=20*cos(phi)
fill triangle 100+20*sin(phi),100+20*cos(phi),100-20*sin(phi),100-20*cos(phi)
,100-80*cos(phi),100+80*sin(phi)
sleep 0.1
loop
This example draws a coloured triangles until you get exhausted.
See also
open window, open printer, line, circle, rectangle
trim$()
Name
trim$() - remove leading and trailing spaces from its argument
Synopsis
a$=trim$(b$)
Description
The trim$-function removes all whitespaces from the left and from the right
end of a string and returns the result. Calling trim$ is equivalent to
calling rtrim$(ltrim$()).
Example
do
input "Continue ? Please answer yes or no: " a$
a$=lower$(trim$(a$))
if (len(a$)>0 and a$=left$("no",len(a$)) exit
loop
This example asks for an answer (yes or no) and removes spaces with trim$ to
make the comparison with the string "no" more bulletproof.
See also
ltrim$, rtrim$
true
Name
true - a constant with the value of 1
Synopsis
okay=true
Description
The constant true can be assigned to variables which will later appear in
conditions (e.g. an if-statement.
true may also be written as TRUE or even TrUe.
Example
input "Please enter a string of all upper letters: " a$
if (is_upper(a$)) print "Okay"
sub is_upper(a$)
if (a$=upper$(a$)) return true
return false
end sub
See also
false
U
Table of Contents
until - end a repeat-loop
upper$() - convert a string to upper case
using - Specify the format for printing a number
until
Name
until - end a repeat-loop
Synopsis
repeat
...
until (...)
Description
The until-keyword ends a loop, which has been introduced by the
repeat-keyword. until requires a condition in braces (or an expression, see
here for details) as an argument; the loop will continue until this
condition evaluates to true.
Example
c=1
s=1
repeat
l=c
s=-(s+sig(s))
c=c+1/s
print c
until(abs(l-c)<0.000001)
This program calculates the sequence 1/1-1/2+1/3-1/4+1/5-1/6+1/7-1/8+ ... ;
please let me know, if you know against which value this converges.
See also
repeat
upper$()
Name
upper$() - convert a string to upper case
Synopsis
u$=upper$(a$)
Description
The upper$-function accepts a single string argument and converts it to all
upper case.
Example
line input "Please enter a sentence without the letter 'e': " l$
p=instr(upper$(l$),"E")
if (p) then
l$=lower$(l$)
mid$(l$,p,1)="E"
print "Hey, you are wrong, see here!"
print l$
else
print "Thanks."
endif
This program asks for a sentence and marks the first (if any) occurence of
the letter 'e' by coverting it to upper case (in contrast to the rest of the
sentence, which is converted to lower case).
See also
lower$
using
Name
using - Specify the format for printing a number
Synopsis
print a using "##.###"
print a using("##.###",",.")
Description
The using-keyword may appear as part of the print-statement and specifies
the format (e.g. the number of digits before and after the decimal dot),
which should be used to print the number.
The possible values for the format argument ("##.###" in the synopsis above)
are described within the entry for the str$-function; especially the second
line in the synopsis (print a using("##.###",",.")) will become clear after
referring to str$. In fact the using clause is closely related to the
str$-function; the former can always be rewritten using the latter; i.e.
print foo using bar$ is always equivalent to print str$(foo,bar$). Therefore
you should check out str$ to learn more.
Example
for a=1 to 10
print sqrt(ran(10000*a)) using "#########.#####"
next a
This example prints a column of square roots of random number, nicely
aligned at the decimal dot.
See also
print, str$
V
Table of Contents
val() - converts a string to a number
val()
Name
val() - converts a string to a number
Synopsis
x=val(x$)
Description
The val-function checks, if the start of its string argument forms a
floating point number and then returns this number. The string therefore has
to start with digits (only whitespace infront is allowed), otherwise the
val-function returns zero.
Example
input "Please enter a length, either in inches (in) or centimeters (cm) " l$
if (right$(l$,2)="in") then
l=val(l$)*2.51
else
l=val(l$)
print "You have entered ",l,"cm."
This example queries for a length and checks, if it has been specified in
inches or centimeters. The length is then converted to centimeters.
See also
str$
W
Table of Contents
wait - pause, sleep, wait for the specified number of seconds
wend - end a while-loop
while - start a while-loop
window origin - move the origin of a window
wait
Name
wait - pause, sleep, wait for the specified number of seconds
Synopsis
wait 4
Description
The wait-command has many different names: You may write pause, sleep or
wait interchangeable; whatever you write, yabasic will always do exactly the
same.
Therefore you should refer to the entry for the pause-function for further
information.
wend
Name
wend - end a while-loop
Synopsis
while(a<b)
...
wend
Description
The wend-keyword marks the end of a while-loop. Please see the while-keyword
for more details.
wend can be written as end while or even end-while.
Example
line input "Please enter a sentence: " a$
p=instr(a$,"e")
while(p)
mid$(a$,p,1)="E"
p=instr(a$,"e")
wend
print a$
This example reads a sentence and converts every occurence of the letter e
into uppercase (E).
See also
while (which is just the following entry).
while
Name
while - start a while-loop
Synopsis
while(...)
...
wend
Description
The while-keyword starts a while-loop, i.e. a loop that is excuted as long
as the condition (which is specified in braces after the keyword while)
evaluates to true.
Note, that the body of such a while-loop will not be executed at all, if the
condition following the while-keyword is not true initially.
If you want to leave the loop prematurely, you may use the break-statement.
Example
open #1,"foo"
while(!eof(1))
line input #1 a$
print a$
wend
This program reads the file foo and prints it line by line.
See also
until, break, wend, do
window origin
Name
origin - move the origin of a window
Synopsis
open window 200,200
origin "cc"
Description
The origin-command applies to graphic windows and moves the origin of the
coordinate system to one of nine point within the window. The normal
position of the origin is in the upper left corner of the window; however in
some cases this is inconvenient and moving the origin may save you from
substracting a constant offset from all of your coordinates.
However, you may not move the origin to an arbitrary position; in horizontal
possition there are only three positions: left, center and right, which are
decoded by the letters l, c and r. In vertical position the allowed
positions are top, center and bottom; encoded by the letters t, c and b.
Taking the letters together, you arrive at a string, which might be passed
as an argument to the command; e.g. "cc" or "rt".
Example
100,100
open window 200,200
window origin "cc"
circle 0,0,60
This example draws a circle, centered at the center of the window.
See also
open window
X
Table of Contents
xor() - compute the exclusive or
xor()
Name
xor() - compute the exclusive or
Synopsis
x=xor(a,b)
Description
The xor computes the bitwise exclusive or of its two numeric arguments. To
understand the result, both arguments should be viewed as binary numbers
(i.e. a series of 0 and 1); a bit of the result will then be 1, if exactly
one argument has a 1 and the other has a 0 at this position in their binary
representation.
Note, that both arguments are silently converted to integer values and that
negative numbers have their own binary representation and may lead to
unexpected results when passed to and.
Example
print xor(7,4)
This will print 3. This result is obvious, if you note, that the binary
representation of 7 and 4 are 111 and 100 respectively; this will yield 011
in binary representaion or 2 as decimal.
The eor-function is the same as the xor function; both are synonymous;
however they have each their own description, so you may check out the entry
of eor for a slightly different view.
See also
and, or, eor, not
Special characters
Table of Contents
# - either a comment or a marker for a file-number
// - starts a comment
@ - synonymous to at
: - separate commands from each other
; - suppress the implicit newline after a print-statement
** or ^ - raise its first argument to the power of its second
#
Name
# - either a comment or a marker for a file-number
Synopsis
# This is a comment, but the line below not !
open #1,"foo"
Description
The hash ('#') has two totally unrelated uses:
* A hash might appear in commands related with file-io. yabasic uses
simple numbers to refer to open files (within input, print, peek or
eof). In those commands the hash may precede the number, which species
the file. Please see those commands for further information and
examples; the rest of this entry is about the second use (as a comment).
* As the very first character within a line, a hash introduces comments
(similar to rem).
'#' as a comment is common in most scripting languages and has a special use
under Unix: If the very first line of any Unix-program begins with the
character sequence '#!' ("she-bang", no spaces allowed), the rest of the
line is taken as the program that should be used to execute the script. I.e.
if your yabasic-program starts with '#!/usr/local/bin/yabasic', the program
/usr/local/bin/yabasic will be invoked to execute the rest of the program.
As a remark for windows-users: This mechanism ensures, that yabasic will be
invoked to execute your program; the ending of the file (e.g. .yab) will be
ignored by Unix.
Example
# This line is a valid comment
print "Hello " : # But this is a syntax error, because
print "World!" : # the hash is not the first character !
Note, that this example will produce a syntax error and is not a valid
program !
See also
input, print, peek or eof, //, rem
//
Name
// - starts a comment
Synopsis
// This is a comment !
Description
The double-slash ('//') is (besides REM and '#') the third way to start a
comment. '//' is the latest and greatest in the field of commenting and
allows yabasic to catch up with such cool languages like C++ and Java.
Example
// Another comment.
print "Hello world !" // Another comment
Unlike the example given for '#' this example is syntactically correct and
will not produce an error.
See also
#, rem
@
Name
@ - synonymous to at
Synopsis
clear screen
print @(a,b)
Description
As '@' is simply a synonym for at, please see at for further information.
See also
at
:
Name
: - separate commands from each other
Synopsis
print "Hello ":print "World"
Description
The colon (':') separates multiple commands on a single line.
The colon and the newline-character have mostly the same effect, only that
the latter, well, starts a new line too. The only other difference is their
effect within the (so-called) short if, which is an if-statement without the
keyword then. Please see the entry for if for more details.
Example
if (a<10) print "Hello ":print "World !"
This example demonstrates the difference between colon and newline as
described above.
See also
if
;
Name
; - suppress the implicit newline after a print-statement
Synopsis
print "foo",bar;
Description
The semicolon (';') may only appear at the last position within a
print-statement. It supresses the implicit newline, which yabasic normally
adds after each print-statement.
Put another way: Normally the output of each print-statement appears on a
line by itself. If you rather want the output of many print-statements to
appear on a single line, you should end the print-statement with a
semicolon.
Example
print "Hello ";:print "World !"
This example prints Hello World ! in a single line.
See also
print
** or ^
Name
** or ^ - raise its first argument to the power of its second
Synopsis
print 2**b
print 3^4
Description
** (or ^, which is an exact synonym), is the arithmetic operator of
exponentiation; it requires one number to its left and a second one to its
right; ** then raises the first argument to the power of the second and
returns the result. The result will only be computed if it yields a real
number (as opposed to a complex number); this means, that the power can not
be computed, if the first argument is negative and the second one is
fractional. On the other hand, the second argument can be fractional, if the
first one ist positive; this means, that ** may be used to compute arbitrary
roots: e.g. x**0.5 computes the square root of x.
Example
print 2**0.5
See also
sqrt
Chapter 7. A grab-bag of some general concepts and terms
Table of Contents
Logical shortcuts
Conditions and expressions
References on arrays
Specifying Filenames under Windows
Escape-sequences
Creating a standalone program from your yabasic-program
This chapter presents some general concepts and terms, which deserve a
description on their own, but are not associated with a single command or
function in yabasic. Most of these topics do not lend themselves to be read
alone, rather they might be read (or skimmed) as background material if an
entry from the alphabetical list of commands refers to them.
Logical shortcuts
Logical shortcuts are no special language construct and there is no keyword
for them; they are just a way to evaluate logical expressions. Logical
expressions (i.e. a series of conditions or comparisons joined by and or or)
are only evaluated until the final result of the expression can be
determined. An example:
if (a<>0 and b/a>2) print "b is at least twice as big as a"
The logical expression a<>0 and b/a>2 consists of two comparisons, both of
which must be true, if the print statement should be executed. Now, if the
first comparison (a<>0) is false, the whole logical expression can never be
true and the second comparison (b/a>2) need not be evaluated.
This is exactly, how yabasic behaves: The evaluation of a composed logical
expressions is terminated immediately, as soon as the final result can be
deduced from the already evaluated parts.
In practice, this has the following consequences:
* If two or more comparisons are joined with and and one comparison
results in false, the logical expression is evaluated no further and the
overall result is false.
* If two or more comparisons are joined with or and one comparison results
in true, the logical expression is evaluated no further and the result
is true.
"Nice, but whats this good for ?", I hear you say. Well, just have another
look at the example, especially the second comparison (b/a>2); deviding b by
a is potentially hazardous: If a equals zero, the expression will cause an
error and your program will terminate. To avoid this, the first part of the
comparison (a<>0) checks, if the second one can be evaluated without risk.
This pre-checking is the most common usage and primary motivation for
logical shortcuts (and the reason why most programming languages implement
them).
Conditions and expressions
Well, bottomline there is no difference or distinction between conditions
and expressions, at least as yabasic is concerned. So you may assign the
result of comparisons to variables or use an arithmetic expression or a
simple variable within a condition (e.g. within an if-statement). So the
constructs shown in the example below are all totally valid:
input "Please enter a number between 1 and 10: " a
rem Assigning the result of a comparison to a variable
okay=a>=1 and a<=10
rem Use a variable within an if-statement
if (not okay) error "Wrong, wrong !"
So conditions and expressions are really the same thing (at least as long as
yabasic is concerned). Therefore the terms conditions and expression can
really be used interchangeably, at least in theory. In reality the term
condition is used in connection with if or while whereas the term expression
tends to be used more often within arithmetic context.
References on arrays
References on arrays are the only way to refer to an array as a whole and to
pass it to subroutines or functions like arraydim or arraysize. Whereas (for
example) a(2) designates the second element of the array a, a() (with empty
braces) refers to the array a itself. a() is called an array reference.
If you pass an array reference to one of your own subroutines, you need to
be aware, that the subroutine will be able to modify the array you have
passed in. So passing an array reference does not create a copy of the
array; this has some interesting consequences:
* Speed and space: Creating a copy of an array would be a time- and
resourceconsuming operation; passing just a reference is cheap and fast.
* Returning many values: A subroutine, that wants to give back more than
one value, may require an array reference among its arguments and then
store its many return values within this array. This is the only way to
return more than one value from a subroutine.
Specifying Filenames under Windows
As you probably know, windows uses the character '\' to separate the
directories within a pathname; an example would be C:\yabasic\yabasic.exe
(the usual location of the yabasic executable). However, the very same
character '\' is used to contstruct escape sequences, not only in yabasic
but in most other programming languages.
Therefore the string "C:\t.dat" does not specify the file t.dat within the
directory C:; this is because the sequence '\t' is translated into the
tab-character. To specify this filename, you need to use the string
"C:\\t.dat" (note the double slash '\\').
Escape-sequences
Escape-sequences are the preferred way of specifying 'special' characters.
They ar intoduced by the '\'-character and followed by one of a few regular
letters, e.g. '\n' or '\r' (see the table below).
Escape-sequences may occur within any string at any position; they are
replaced at parsetime (opposed to runtime), i.e. as soon as yabasic
discovers the string, with their corresponding special character. As a
consequence of this len("\a") returns 1, because yabasic replaces "\a" with
the matching special character just before the program executes.
Table 7.1. Escape sequences
Escape Seqence Matching special character
\n newline
\t tabulator
\v vertical tabulator
\b backspace
\r carriage return
\f formfeed
\a alert (i.e. a beeping sound)
\\ backslash
\' single quote
\" double quote
\xHEX chr$(HEX) (see below)
Note, that an escape sequences of the form \xHEX allows to encode arbitrary
characters as long as you know their position (as a hex-number) within the
ascii-charset: For example \x012 is transformed into the character chr$(18)
(or chr$(dec("12",16)). Note that \x requires a hexa-decimal number (and the
hexa-decimal string "12" corresponds to the decimal number 18).
Creating a standalone program from your yabasic-program
Note
The bind-feature, which is described below, is at an experimental stage
right now. It works (at least for me !) under Windows and Linux, but I
cannot even promise it for other variants of Unix. However, if it does not
work for your Unix, I will at least try to make it work, if you give me
sufficient information of your system.
Sometimes you may want to give one of your yabasic-programs to other people.
However, what if those other people do not have yabasic installed ? In that
case you may create a standalone-program from your yabasic-program, i.e. an
executable, that may be executed on its own, standalone, even (and
especially !) on computers, that do not have yabasic installed. Having
created a standalone program, you may pass it around like any other program
(e.g. one written in C) and you can be sure that your program will execute
right away.
Such a standalone-program is simply created by copying the full
yabasic-interpreter and your yabasic-program (plus all the libraries it does
import) together into a single, new program, whose name might be chosen at
will (under windows of course it should have the ending .exe). If you decide
to create a standalone-program, there are three bits in yabasic, that you
may use:
* The bind-command, which does the actual job of creating the standalone
program from the yabasic-interpreter and your program.
* The command-line Option -bind (available under windows and Unix), which
does the same from the command-line.
* The special peek("isbound"), which may be used to check, if the
yabasic-program containing this peek is bound to the interpreter as part
of a standalone program.
With these bits you know enough to create a standalone-program. Actually
there are two ways to do this: on the commandline and from within your
program.
Creating a standalone-program from the commandline
Let's say you have the following very simple program within the file
foo.yab:
print "Hello World !"
Normally you would start this yabasic-program by typing yabasic foo.yab and
as a result the string Hello World ! would appear on your screen. However,
to create a standalone-program from foo.yab you would type:
yabasic-bind foo.exe foo.yab
This command does not execute your program foo.yab but rather create a
standalone-program foo.exe. Note: under Unix you would probably name the
standalone program foo or such, omitting the windows-specific ending .exe.
Yabasic will confirm by printing something like: ---Info: Successfully bound
'yabasic' and 'foo.yab' into 'foo.exe'.
After that you will find a program foo.exe (which must be made executable
with the chmod-command under Unix first). Now, executing this program
foo.exe (or foo under Unix) will produce the output Hello World !.
This newly created program foo.exe might be passed around to anyone, even if
he does not have yabasic installed.
Creating a standalone-program from within your program
It is possible to write a yabasic-program, that binds itself to the
yabasic-interpreter. Here is an example:
if (!peek("isbound")) then
bind "foo"
print "Successfully created the standalone executable 'foo' !"
exit
endif
print "Hello World !"
If you run this program (which may be saved in the file foo.yab) via yabasic
foo.yab, the peek("isbound") in the first line will check, if the program is
already part of a standalone-program. If not (i.e. if the
yabasic-interpreter and the yabasic-program are seperate files) the
bind-command will create a standalone program foo containing both. As a
result you would see the output Successfully created the standalone
executable 'foo' !. Note: Under Windows you would probably choose the
filename foo.exe.
Now, if you run this standalone executable foo (or foo.exe), the very same
yabasic-program that is shown above will be executed again. However, this
time the peek("isbound") will return TRUE and therefore the condition of the
if-statement is false and the three lines after then are not executed.
Rather the last print-statement will run, and you will see the output Hello
World !.
That way a yabasic-program may turn itself into a standalone-program.
Downsides of creating a standalone program
Now, before you go out and turn all your yabasic-programs into standalone
programs, please take a second to consider the downsides of doing so:
* The new standalone program will be at least as big as the interpreter
itself, so you need to pass a few hundred kilobytes around, just to save
people from having to install yabasic themselves.
* There is no easy way to extract your yabasic-program from within the
standalone program: If you ever want to change it, you need to have it
around seperately.
* If a new version of yabasic becomes available, again you need to
recreate all of your standalone programs to take advantage of bugfixes
and improvements.
So, beeing able to create a standalone program is certainly a good thin, but
certainly not a silver bullet.
See also
The bind-command, the peek-function and the commandline options for Unix and
Windows.
Chapter 8. A few example programs
Table of Contents
A very simple program
The demo of yabasic
A very simple program
The program below is a very simple program:
repeat
input "Please enter the first number, to add " a
input "Please enter the second number, to add " b
print a+b
until(a=0 and b=0)
This program requests two numbers, which it than adds. The process is
repeated until you enter zero (or nothing) twice.
The demo of yabasic
The listing below is the demo of yabasic. Note, that parts of this demo have
been written before some of the more advanced features (e.g subroutines) of
yabasic have been implemented. So please do not take this as a particular
good example of yabasic-code.
//
// This program demoes yabasic
//
// Check, if screen is large enough
clear screen
sw=peek("screenwidth"):sh=peek("screenheight")
if (sw<78 or sh<24) then
print
print " Sorry, but your screen is to small to run this demo !"
print
end
endif
sw=78:sh=24
// Initialize everything
restore mmdata
read mmnum:dim mmtext$(mmnum)
for a=1 to mmnum:read mmtext$(a):next a
// Main loop selection of demo
ysel=1
label mainloop
clear screen
print colour("cyan","magenta") at(7,2) "################################"
print colour("cyan","magenta") at(7,3) "################################"
print colour("cyan","magenta") at(7,4) "################################"
print colour("yellow","blue") at(8,3) " This is the demo for yabasic "
yoff=7
for a=1 to mmnum
if (a=mmnum) then ydisp=1:else ydisp=0:fi
if (a=ysel) then
print colour("blue","green") at(5,yoff+ydisp+a) mmtext$(a);
else
print at(5,yoff+ydisp+a) mmtext$(a);
endif
next a
print at(3,sh-3) "Move selection with CURSOR KEYS (or u and d),"
print at(3,sh-2) "Press RETURN or SPACE to choose, ESC to quit."
do // loop for keys pressed
rev=1
do // loop for blinking
k$=inkey$(0.4)
if (k$="") then
if (ysel=mmnum) then
if (rev=1) then
print colour("blue","green") at(5,yoff+mmnum+1) mmtext$(mmnum);
rev=0
else
print colour("yellow","red") at(5,yoff+mmnum+1) mmtext$(mmnum);
rev=1
endif
endif
else // key has been pressed, leave loop
break
endif
loop // loop for blinking
yalt=ysel
if (k$="up" or k$="u") then
if (ysel=1) then ysel=mmnum else ysel=ysel-1 fi
redraw():heal():continue
fi
if (k$="down" or k$="d") then
if (ysel=mmnum) then ysel=1 else ysel=ysel+1 fi
redraw():heal():continue
fi
if (k$=" " or k$="enter" or k$="right") then
on ysel gosub overview,bitmap,tetraeder,endit
goto mainloop
fi
if (k$="esc") then
endit()
fi
beep
print at(3,sh-5) "Invalid key: ",k$," "
loop // loop for keys pressed
// redraw line
sub redraw()
if (yalt=mmnum) then ydisp=1:else ydisp=0:fi
print at(5,yoff+yalt+ydisp) mmtext$(yalt);
if (ysel=mmnum) then ydisp=1:else ydisp=0:fi
print colour("blue","green") at(5,yoff+ysel+ydisp) mmtext$(ysel);
return
end sub
// erase a line
sub heal()
print at(3,sh-5) " "
return
end sub
// Go here to exit
label endit
print at(3,sh-8) "Hope you liked it ...\n ";
exit
return
// Present a short overview
label overview
clear screen
print
print " Yabasic is a quite traditional basic: It comes with"
print " print, input, for-next-loops, goto, gosub, while and"
print " repeat. It has user defined procedures and libraries,"
print " however, it is not object oriented.\n"
print " Yabasic makes it easy to open a window, draw lines"
print " and print the resulting picture.\n"
print " Yabasic programs are interpreted and run under Unix"
print " and Windows. The Yabasic interpreter (around 200K)"
print " and any Yabasic program can be glued together to"
print " form a standalone executable.\n"
print " Yabasic is free software, i.e. subject to the"
print " GNU copyright.\n"
print "\n\n\n While you read this, I am calculating prime numbers,\n"
print " Press any key to return to main menu ..."
can=1
print at(6,17) "This is a prime number: "
label nextcan
can=can+2
for i=2 to sqrt(can):if (frac(can/i)=0) then goto notprime:fi:next i
print at(32,17) can;
label notprime
if (lower$(inkey$(0))<>"") then
print at(10,sh) "Wrappinging around once ...";
for x=1 to sw
a$=getscreen$(0,0,1,sh-2)
b$=getscreen$(1,0,sw-1,sh-2)
putscreen b$,0,0
putscreen a$,sw-1,0
next x
sleep 2
return
fi
goto nextcan
// Show some animated bitmaps
label bitmap
clear screen
print
print "Yabasic offers some commands for drawing simple grafics."
print reverse at(5,12) " Press any key to return to main menu ... "
n=20
open window 400,400
for b=20 to 0 step -1
color 255-b*12,0,b*12
fill circle 200,200,b
next b
c$=getbit$(179,179,221,221)
for a=1 to 2000
color ran(255),ran(255),ran(255)
x=ran(500)-100:y=ran(500)-100
fill rectangle ran(500)-100,ran(500)-100,ran(500)-100,ran(500)-100
next a
x=200:y=200:phi=ran(2*pi):dx=2*sin(phi):dy=2*cos(phi)
o$=""
count=0
label pong
count=count+1
if (o$<>"") putbit o$,xo-2,yo-2
if (count>1000) then
phi=ran(2*pi):dx=2*sin(phi):dy=2*cos(phi)
sleep 2
count=0
endif
xo=x:yo=y
x=x+dx:y=y+dy
o$=getbit$(x-2,y-2,x+46,y+46)
putbit c$,x,y,"t"
if (x<0 or x>360) dx=-dx
if (y<0 or y>360) dy=-dy
if (inkey$(0)<>"") then
close window
return
endif
goto pong
return
label tetraeder
open window 400,400
clear window
clear screen
print reverse at(5,12) " Press any key to return to main menu ... "
dim opoints(4,3)
restore points
for n=1 to 4:for p=1 to 3:read opoints(n,p):next p:next n
dim triangles(4,3)
restore triangles
for n=1 to 4:for p=1 to 3:read triangles(n,p):next p:next n
phi=0:dphi=0.1:psi=0:dpsi=0.05
dim points(4,3)
r=60:g=20
dr=0.5:dg=1.2:db=3
label main
phi=phi+dphi
psi=psi+dpsi
for n=1 to 4
points(n,1)=opoints(n,1)*cos(phi)-opoints(n,2)*sin(phi)
points(n,2)=opoints(n,2)*cos(phi)+opoints(n,1)*sin(phi)
p2= points(n,2)*cos(psi)-opoints(n,3)*sin(psi)
points(n,3)=opoints(n,3)*cos(psi)+ points(n,2)*sin(psi)
points(n,2)=p2
next n
r=r+dr:if (r<0 or r>60) dr=-dr
g=g+dg:if (g<0 or g>60) dg=-dg
b=b+db:if (b<0 or b>60) db=-db
dm=dm+0.01
m=120-80*sin(dm)
for n=1 to 4
p1=triangles(n,1)
p2=triangles(n,2)
p3=triangles(n,3)
n1=points(p1,1)+points(p2,1)+points(p3,1)
n2=points(p1,2)+points(p2,2)+points(p3,2)
n3=points(p1,3)+points(p2,3)+points(p3,3)
if (n3>0) then
sp=n1*0.5-n2*0.7-n3*0.6
color 60+r+30*sp,60+g+30*sp,60+b+30*sp
fill triangle 200+m*points(p1,1),200+m*points(p1,2),200+m*points(p2,1),20
0+m*points(p2,2),200+m*points(p3,1),200+m*points(p3,2)
endif
next n
if (inkey$(0.1)<>"") close window:return
clear window
goto main
label points
data -1,-1,+1, +1,-1,-1, +1,+1,+1, -1,+1,-1
label triangles
data 1,2,4, 2,3,4, 1,3,4, 1,2,3
// Data section ...
label mmdata
// Data for main menu: Number and text of entries in main menu
data 4
data " Yabasic in a nutshell "
data " Some grafics "
data " A rotating Tetraeder "
data " Exit this demo "
Chapter 9. The Copyright of yabasic
yabasic may be copied only under the terms of the Artistic License or the
GNU General Public License (GPL), both of which are distributed with
yabasic.
[Can't you make up your mind ?!], I hear you say. Umm, well yes. In fact I
do not want to read or try to understand them both, so I have put the burden
on you (grin). However, I think that the Artistic License is more liberal
and gives you more rights and you should choose it; on the other hand the
GPL is more widely known and a lot of software is distributed under its
terms.
Here is a list of things that are possible under the terms of the Artistic
License:
* Put yabasic on your own homepage or CD and even charge for the service
of distributing yabasic.
* Write your own yabasic-programs, pack your program and yabasic into a
package and sell the whole thing.
* Modify yabasic and add or remove features, sell the modified version.
AUTHOR
Marc-Oliver Ihm, with the input and suggestions from many others.
SEE ALSO
yabasic.htm - for the hyperlinked version of the text that is presented
above.
www.yabasic.de - for further information about yabasic.
BUGS
Still some.
yabasic(1)
