nextafter(3) — Linux manual page


nextafter(3)            Library Functions Manual            nextafter(3)

NAME         top

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

LIBRARY         top

       Math library (libm, -lm)

SYNOPSIS         top

       #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

           _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         top

       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         top

       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

ERRORS         top

       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         top

       For an explanation of the terms used in this section, see
       │ Interface                           Attribute     Value   │
       │ nextafter(), nextafterf(),          │ Thread safety │ MT-Safe │
       │ nextafterl(), nexttoward(),         │               │         │
       │ nexttowardf(), nexttowardl()        │               │         │

STANDARDS         top

       C11, POSIX.1-2008.

       This function is defined in IEC 559 (and the appendix with
       recommended functions in IEEE 754/IEEE 854).

HISTORY         top

       C99, POSIX.1-2001.

BUGS         top

       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         top


COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                   nextafter(3)

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