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Manual

nextafter

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
STANDARDS
HISTORY
BUGS
SEE ALSO

NAME

nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl - floating-point number manipulation

LIBRARY

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 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 floating-point 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

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).

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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)