## table of contents

REMAINDER(3) | Linux Programmer's Manual | REMAINDER(3) |

# NAME¶

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

# 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);

Link with *-lm*.

**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 |

# 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 *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¶

# COLOPHON¶

This page is part of release 5.13 of the Linux *man-pages*
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/man-pages/.

2021-03-22 |