# REMAINDER

Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
Index

## NAME

drem, dremf, dreml, remainder, remainderf, remainderl - floating-point 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);```

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 xby y. The return value is x-n*y, where nis the value x / y, rounded to the nearest integer. If the absolute value of x-n*yis 0.5, nis 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 xor yis a NaN, a NaN is returned.

If xis an infinity, and yis not a NaN, a domain error occurs, and a NaN is returned.

If yis zero, and xis 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
errnois set to EDOM(but see BUGS). An invalid floating-point exception (FE_INVALID) is raised.
These functions do not set errnofor this case.
Domain error: y is zeroerrno
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(), remainderl() Thread safety MT-Safe

## CONFORMING TO

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 floatand long doublevariants 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, errnowas not set to EDOMfor the domain error that occurs when xis an infinity and yis not a NaN. errno was not set

## EXAMPLE

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

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

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
CONFORMING TO
BUGS
EXAMPLE