
NEXTAFTER(3) Linux Programmer's Manual NEXTAFTER(3)
NAME
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl  floatingpoint
number manipulation
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);
Link with lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
nextafter():
_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 500 
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED  _ISOC99_SOURCE 
_POSIX_C_SOURCE >= 200112L;
or cc std=c99
nextafterf(), nextafterl():
_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 600  _ISOC99_SOURCE 
_POSIX_C_SOURCE >= 200112L;
or cc std=c99
nexttoward(), nexttowardf(), nexttowardl():
_XOPEN_SOURCE >= 600  _ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L;
or cc std=c99
DESCRIPTION
The nextafter(), nextafterf(), and nextafterl() functions return the next representable
floatingpoint value following x in the direction of y. If y is less than x, these func
tions will return the largest representable number less than x.
If x equals y, the functions return y.
The nexttoward(), nexttowardf(), and nexttowardl() functions do the same as the corre
sponding nextafter() functions, except that they have a long double second argument.
RETURN VALUE
On success, these functions return the next representable floatingpoint value after x in
the direction of y.
If x equals y, then y (cast to the same type as x) is returned.
If x or y is a NaN, a NaN is returned.
If x is finite, and the result would overflow, a range error occurs, and the functions
return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with the correct mathematical
sign.
If x is not equal to y, and the correct function result would be subnormal, zero, or
underflow, a range error occurs, and either the correct value (if it can be represented),
or 0.0, is returned.
ERRORS
See math_error(7) for information on how to determine whether an error has occurred when
calling these functions.
The following errors can occur:
Range error: result overflow
An overflow floatingpoint exception (FE_OVERFLOW) is raised.
Range error: result is subnormal or underflows
An underflow floatingpoint exception (FE_UNDERFLOW) is raised.
These functions do not set errno.
ATTRIBUTES
Multithreading (see pthreads(7))
The nextafter(), nextafterf(), nextafterl(), nexttoward(), nexttowardf(), and nextto
wardl() functions are threadsafe.
CONFORMING TO
C99, POSIX.12001. This function is defined in IEC 559 (and the appendix with recommended
functions in IEEE 754/IEEE 854).
BUGS
In glibc version 2.5 and earlier, these functions do not raise an underflow floatingpoint
(FE_UNDERFLOW) exception when an underflow occurs.
SEE ALSO
nearbyint(3)
COLOPHON
This page is part of release 3.55 of the Linux manpages project. A description of the
project, and information about reporting bugs, can be found at
http://www.kernel.org/doc/manpages/.
GNU 20130902 NEXTAFTER(3) 
