REMAINDER
Section: Linux Programmer's Manual (3)
Updated: 20200609
Page Index
NAME
drem, dremf, dreml, remainder, remainderf, remainderl  floatingpoint 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():

_ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L
 _XOPEN_SOURCE >= 500
 /* Since glibc 2.19: */ _DEFAULT_SOURCE
 /* Glibc versions <= 2.19: */ _BSD_SOURCE  _SVID_SOURCE
remainderf(),
remainderl():

_ISOC99_SOURCE  _POSIX_C_SOURCE >= 200112L
 /* Since glibc 2.19: */ _DEFAULT_SOURCE
 /* Glibc versions <= 2.19: */ _BSD_SOURCE  _SVID_SOURCE
drem(),
dremf(),
dreml():

/* Since glibc 2.19: */ _DEFAULT_SOURCE
 /* Glibc versions <= 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 floatingpoint 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 floatingpoint exception
(FE_INVALID)
is raised.

These functions do not set
errno
for this case.
 Domain error: y is zeroerrno

is set to
EDOM.
An invalid floatingpoint 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  MTSafe

CONFORMING TO
The functions
remainder(),
remainderf(),
and
remainderl()
are specified in C99, POSIX.12001, and POSIX.12008.
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)
COLOPHON
This page is part of release 5.10 of the Linux
manpages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/manpages/.