- floating-point number manipulation

       #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 (see feature_test_macros(7)):

           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
           _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

       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.

       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.
              An overflow floating-point exception (FE_OVERFLOW) is raised.

       Range error: result is subnormal or underflows
              An underflow floating-point exception (FE_UNDERFLOW) is raised.

       These functions do not set errno.

   Multithreading (see pthreads(7))
       The  nextafter(),  nextafterf(),  nextafterl(),  nexttoward(),  nextto-
       wardf(), and nexttowardl() functions are thread-safe.

       C99, POSIX.1-2001.  This function is defined in IEC 559 (and the appen-
       dix with recommended functions in IEEE 754/IEEE 854).

       In  glibc  version  2.5  and  earlier,  these functions do not raise an
       underflow floating-point (FE_UNDERFLOW)  exception  when  an  underflow


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GNU                               2013-09-02                      NEXTAFTER(3)
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