NEXTAFTER(P) POSIX Programmer's Manual NEXTAFTER(P)NAME
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl
- next representable floating-point number
SYNOPSIS
#include <math.h>
double nextafter(double x, double y);
float nextafterf(float x, float y);
long double nextafterl(long double x, long double y);
double nexttoward(double x, long double y);
float nexttowardf(float x, long double y);
long double nexttowardl(long double x, long double y);
DESCRIPTION
The nextafter(), nextafterf(), and nextafterl() functions shall compute
the next representable floating-point value following x in the direc‐
tion of y. Thus, if y is less than x, nextafter() shall return the
largest representable floating-point number less than x. The
nextafter(), nextafterf(), and nextafterl() functions shall return y if
x equals y.
The nexttoward(), nexttowardf(), and nexttowardl() functions shall be
equivalent to the corresponding nextafter() functions, except that the
second parameter shall have type long double and the functions shall
return y converted to the type of the function if x equals y.
An application wishing to check for error situations should set errno
to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
functions. On return, if errno is non-zero or fetestexcept(FE_INVALID
| FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
occurred.
RETURN VALUE
Upon successful completion, these functions shall return the next rep‐
resentable floating-point value following x in the direction of y.
If x== y, y (of the type x) shall be returned.
If x is finite and the correct function value would overflow, a range
error shall occur and ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (with the
same sign as x) shall be returned as appropriate for the return type of
the function.
If x or y is NaN, a NaN shall be returned.
If x!= y and the correct function value is subnormal, zero, or under‐
flows, a range error shall occur, and either the correct function value
(if representable) or 0.0 shall be returned.
ERRORS
These functions shall fail if:
Range Error
The correct value overflows.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then errno shall be set to [ERANGE]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow
floating-point exception shall be raised.
Range Error
The correct value is subnormal or underflows.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then errno shall be set to [ERANGE]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow
floating-point exception shall be raised.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
On error, the expressions (math_errhandling & MATH_ERRNO) and
(math_errhandling & MATH_ERREXCEPT) are independent of each other, but
at least one of them must be non-zero.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOfeclearexcept() , fetestexcept() , the Base Definitions volume of
IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for
Mathematical Functions, <math.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 NEXTAFTER(P)
