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 (seefeature_test_macros(7)): nextafter(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc -std=c99 nextafterf(), nextafterl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc -std=c99 nexttoward(), nexttowardf(), nexttowardl(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc -std=c99 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 repre- sentable 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, respec- tively, with the correct mathematical sign. If x is not equal to y, and the correct function result would be sub- Range error: result is subnormal or underflows An underflow floating-point exception (FE_UNDERFLOW) is raised. These functions do not set errno. ATTRIBUTES For an explanation of the terms used in this section, seeattributes(7). +-----------------------------+---------------+---------+ |Interface | Attribute | Value | +-----------------------------+---------------+---------+ |nextafter(), nextafterf(), | Thread safety | MT-Safe | |nextafterl(), nexttoward(), | | | |nexttowardf(), nexttowardl() | | | +-----------------------------+---------------+---------+ CONFORMING TO C99, POSIX.1-2001, POSIX.1-2008. 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 ALSOnearbyint(3)COLOPHON This page is part of release 4.04 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/. GNU 2015-04-19NEXTAFTER(3)