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



NAME
       drem, dremf, dreml, remainder, remainderf, remainderl - floating-point remainder function

SYNOPSIS
       #include <math.h>

       /* The C99 versions */
       double remainder(double x, double y);
       float remainderf(float x, float y);
       long double remainderl(long double x, long double y);

       /* Obsolete synonyms */
       double drem(double x, double y);
       float dremf(float x, float y);
       long double dreml(long double x, long double y);

       Link with -lm.

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

       remainder(): _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or cc -std=c99
       remainderf(), remainderl(): _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
       cc -std=c99
       drem(), dremf(), dreml(): _SVID_SOURCE || _BSD_SOURCE

DESCRIPTION
       The remainder() function computes the remainder of dividing x by y.  The return value is x-n*y, where n is  the
       value x / y, rounded to the nearest integer.  If the absolute value of x-n*y is 0.5, n is chosen to be even.

       These functions are unaffected by the current rounding mode (see fenv(3)).

       The drem() function does precisely the same thing.

RETURN VALUE
       On  success,  these functions return the floating-point remainder, x-n*y.  If the return value is 0, it has the
       sign of x.

       If x or y is a NaN, a NaN is returned.

       If x is an infinity, and y is not a NaN, a domain error occurs, and a NaN is returned.

       If y is zero, and x is not a NaN, a domain error occurs, and a NaN is returned.

ERRORS
       See math_error(7) for information on how to determine whether an error has occurred when  calling  these  func-
       tions.

       The following errors can occur:

       Domain error: x is an infinity and y is not a NaN
              An invalid floating-point exception (FE_INVALID) is raised.

              These functions do not set errno for this case.

       Domain error: y is zero
              errno is set to EDOM.  An invalid floating-point exception (FE_INVALID) is raised.

CONFORMING TO
       The functions remainder(), remainderf(), and remainderl() are specified in C99 and POSIX.1-2001.

       The  function drem() is from 4.3BSD.  The float and long double variants dremf() and dreml() exist on some sys-
       tems, such as Tru64 and glibc2.  Avoid the use of these functions in favor of remainder() etc.

BUGS
       The call

           remainder(nan(""), 0);

       returns a NaN, as expected, but wrongly causes a domain error; it should yield a silent NaN.

EXAMPLE
       The call "remainder(29.0, 3.0)" returns -1.

SEE ALSO
       div(3), fmod(3), remquo(3)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                  2009-02-04                      REMAINDER(3)