Name
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl - floating-point number manipulationLibrary
Math library ( libm ", " -lm )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 );
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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
nextafterf() nextafterl()
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 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 floating-point value following x in the direction ofy
. 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 floating-point value after x in the direction ofy
. 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 errno is set to ERANGE .An overflow floating-point exception ( FE_OVERFLOW ) is raised.
Range error: result is subnormal or underflows errno is set to ERANGE .An underflow floating-point exception ( FE_UNDERFLOW ) is raised.
Attributes
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
T} | Thread safety | MT-Safe |
Standards
C11, POSIX.1-2008.This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
History
C99, POSIX.1-2001.Bugs
In glibc 2.5 and earlier, these functions do not raise an underflow floating-point ( FE_UNDERFLOW ) exception when an underflow occurs.Before glibc 2.23 these functions did not set errno
.
See Also
- nearbyint(3)