NEXTAFTER(3)                        Linux Programmer's Manual                        NEXTAFTER(3)



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

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);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       nextafter():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
           _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

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  func‐
       tions 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 corre‐
       sponding 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
              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.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The nextafter(), nextafterf(),  nextafterl(),  nexttoward(),  nexttowardf(),  and  nextto‐
       wardl() functions are thread-safe.

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

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

SEE ALSO
       nearbyint(3)

COLOPHON
       This  page  is  part of release 3.74 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at http://www.kernel.org/doc/man-pages/.



GNU                                         2013-09-02                               NEXTAFTER(3)