NAME¶

nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl - floating-point 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(): nextafterf(), nextafterl(): nexttoward(), nexttowardf(), nexttowardl():

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

An overflow floating-point exception (FE_OVERFLOW) is raised.

Range error: result is subnormal or underflows

An underflow floating-point exception (FE_UNDERFLOW) is raised.

These functions do not set errno.

ATTRIBUTES¶

Multithreading (see pthreads(7))¶

The nextafter(), nextafterf(), nextafterl(), nexttoward(), nexttowardf(), and nexttowardl() functions are thread-safe.

CONFORMING TO¶

C99, POSIX.1-2001. 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 floating-point (FE_UNDERFLOW) exception when an underflow occurs.

SEE ALSO¶

nearbyint(3)

COLOPHON¶

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