nexttowardl(3) Linux Man Page

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). allbox; lbx lb lb T{ nextafter()nextafterf()nextafterl()nexttoward()nexttowardf()nexttowardl()

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.

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