NAME

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

LIBRARY

       Math library (libm, -lm)

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);

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

       remainder():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || _XOPEN_SOURCE >= 500
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       remainderf(), remainderl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       drem(), dremf(), dreml():
           /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

       These  functions  compute  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 functions.

       The following errors can occur:

       Domain error: x is an infinity and y is not a NaN
              errno  is  set  to  EDOM  (but  see  BUGS).   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.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌───────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                      │ Attribute     │ Value   │
       ├───────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │drem(), dremf(), dreml(), remainder(), remainderf(),           │ Thread safety │ MT-Safe │
       │remainderl()                                                   │               │         │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       The   functions   remainder(),  remainderf(),  and  remainderl()  are  specified  in  C99,
       POSIX.1-2001, and POSIX.1-2008.

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

BUGS

       Before glibc 2.15, the call

           remainder(nan(""), 0);

       returned a NaN, as expected, but wrongly caused a  domain  error.   Since  glibc  2.15,  a
       silent NaN (i.e., no domain error) is returned.

       Before glibc 2.15, errno was not set to EDOM for the domain error that occurs when x is an
       infinity and y is not a NaN.

EXAMPLES

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

SEE ALSO

       div(3), fmod(3), remquo(3)