nextafterl (3)
Leading comments
Copyright 2002 Walter Harms (walter.harms@informatik.unioldenburg.de) and Copyright 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpages@gmail.com> %%%LICENSE_START(GPL_NOVERSION_ONELINE) Distributed under GPL %%%LICENSE_END Based on glibc infopages
NAME
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl  floatingpoint number manipulationSYNOPSIS
#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 functions 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 corresponding 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
For an explanation of the terms used in this section, see attributes(7).Interface  Attribute  Value 
nextafter(),
nextafterf(),
nextafterl(), nexttoward(), nexttowardf(), nexttowardl()  Thread safety  MTSafe 