remainder(3) Library Functions Manual remainder(3)
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 in-
teger. 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 at-
tributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│drem(), dremf(), dreml(), remainder(), │ Thread safety │ MT-Safe │
│remainderf(), 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)
Linux man-pages 6.03 2023-02-05 remainder(3)
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