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(),         │ Thread safety │ MT-Safe │
       │nexttowardf(), 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)