plex(1) Pascal lexical analyzer generator plex(1)NAMEplex - The Pascal Lex lexical analyzer generator.
USAGE
lex [options] lex-file[.l] [output-file[.pas]]
OPTIONS-v Verbose: plex generates a readable description of the generated
lexical analyzer, written to lex-file with new extension .lst
-o Optimize: plex optimizes DFA tables to produce a minimal DFA.
DESCRIPTIONplex is a program generator that is used to generate the Turbo Pascal
source code for a lexical analyzer subroutine from the specification of
an input language by a regular expression grammar.
plex parses the source grammar contained in lex-file (with default suf‐
fix .l) and writes the constructed lexical analyzer subroutine to the
specified output-file (with default suffix .pas); if no output file is
specified, output goes to lex-file with new suffix .pas. If any errors
are found during compilation, error messages are written to the list
file (lex-file with new suffix .lst).
The generated output file contains a lexical analyzer routine, yylex,
implemented as:
function yylex : Integer;
This routine has to be called by your main program to execute the lexi‐
cal analyzer. The return value of the yylex routine usually denotes the
number of a token recognized by the lexical analyzer (see the return
routine in the LexLib unit). At end-of-file the yylex routine normally
returns 0.
The code template for the yylex routine may be found in the yylex.cod
file. This file is needed by TP Lex when it constructs the output file.
It must be present either in the current directory or in the directory
from which TP Lex was executed (TP Lex searches these directories in
the indicated order). (NB: For the Linux/Free Pascal version, the code
template is searched in some directory defined at compile-time instead
of the execution path, usually /usr/lib/fpc/lexyacc.)
The TP Lex library (LexLib) unit is required by programs using Lex-gen‐
erated lexical analyzers; you will therefore have to put an appropriate
uses clause into your program or unit that contains the lexical ana‐
lyzer routine. The LexLib unit also provides various useful utility
routines; see the file lexlib.pas for further information.
MORE INFORMATION
For more information, see the documentation that comes with plex and
yacc.
AUTHOR
Albert Graeff (<ag@muwiinfa.geschichte.uni-mainz.de>, <Dr.Graef@t-
online.de>)
SEE ALSOppc386(1)pyacc(1)Free Pascal 10 Jan 2000 plex(1)
