nextafter(3) Library Functions Manual nextafter(3)
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl - floating-point number manipulation
Math library (libm, -lm)
#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
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.
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.
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.
For an explanation of the terms used in this section, see attributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │nextafter(), nextafterf(), │ Thread safety │ MT-Safe │ │nextafterl(), nexttoward(), │ │ │ │nexttowardf(), nexttowardl() │ │ │ └──────────────────────────────────────┴───────────────┴─────────┘
C11, POSIX.1-2008. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
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.
nearbyint(3) Linux man-pages 6.04 2023-03-30 nextafter(3)
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