# remainder - Man Page

floating-point remainder function

## Library

Math library (*libm*, *-lm*)

## Synopsis

#include <math.h>/* The C99 versions */double remainder(doublex, doubley); float remainderf(floatx, floaty); long double remainderl(long doublex, long doubley);/* Obsolete synonyms */double drem(doublex, doubley); float dremf(floatx, floaty); long double dreml(long doublex, long doubley);

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 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 attributes(7).

Interface | Attribute | Value |
---|---|---|

drem(), dremf(), dreml(), remainder(), remainderf(), remainderl() | Thread safety | MT-Safe |

## 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

## Referenced By

div(3), fma(3), fmod(3), remquo(3).

The man pages drem(3), dremf(3), dreml(3), remainderf(3) and remainderl(3) are aliases of remainder(3).