nextafter (3)  Linux Man Pages
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():

_ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L
 _XOPEN_SOURCE >= 500
 /* Since glibc 2.19: */ _DEFAULT_SOURCE
 /* Glibc versions <= 2.19: */ _BSD_SOURCE  _SVID_SOURCE
nextafterf(), nextafterl():

_ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L
 /* Since glibc 2.19: */ _DEFAULT_SOURCE
 /* Glibc versions <= 2.19: */ _BSD_SOURCE  _SVID_SOURCE
nexttoward(), nexttowardf(), nexttowardl():
 _XOPEN_SOURCE >= 600  _ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L
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 
CONFORMING TO
C99, POSIX.12001, POSIX.12008. 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.COLOPHON
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