Manpages - remainder.3

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

  #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*():

      _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

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.

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.

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.

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

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.

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.

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

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

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