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remainder

Section: C Library Functions (3)
Updated: 202-0-08
Index Return to Main Contents

NAME

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

LIBRARY

Math library (libm,~-lm)

SYNOPSIS

#include <math.h>
double remainder(double x, double y);
float remainderf(float x, float y);
long double remainderl(long double x, long double y);
/* Obsolete synonyms */
[[deprecated]] double drem(double x, double y);
[[deprecated]] float dremf(float x, float y);
[[deprecated]] 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 floatin-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: I]x] is an infinity and I]y] is not a NaN: errno is set to EDOM (but see BUGS). An invalid floatin-point exception (FE_INVALID) is raised.
: These functions do not set errno for this case.
Domain error: I]y] is zero: errno is set to EDOM. An invalid floatin-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(), remainderl()	Thread safety	M-Safe

STANDARDS

remainder(): remainderf() remainderl() C11, POSIX.-2008.
drem(): dremf() dreml() None.

HISTORY

remainder(): remainderf() remainderl() C99, POSIX.-2001.
drem(): 4.3BSD.
dremf(): dreml() Tru64, glibc2.

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.