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).

       ┌──────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                                     │ Attribute     │ Value   │
       ├──────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │nextafter(), nextafterf(), nextafterl(), nexttoward(), nexttowardf(),         │ Thread safety │ MT-Safe │
       │nexttowardl()                                                                 │               │         │
       └──────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

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.

SEE ALSO

       nearbyint(3)