SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

CONFORMING TO

BUGS

EXAMPLE

SEE ALSO

COLOPHON

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

**#include
<math.h>**

/* The C99
versions */

double remainder(double*x***, double**
*y***);
float remainderf(float**

long double remainderl(long double

/* Obsolete
synonyms */

double drem(double*x***, double** *y***);
float dremf(float**

long double dreml(long double

Link with
*−lm*.

Feature Test
Macro Requirements for glibc (see
**feature_test_macros**(7)):

**remainder**():

_SVID_SOURCE || _BSD_SOURCE ||
_XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED ||
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;

or *cc -std=c99*

**remainderf**(),
**remainderl**():

_BSD_SOURCE || _SVID_SOURCE ||
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;

or *cc -std=c99*

**drem**(), **dremf**(),
**dreml**():

_SVID_SOURCE || _BSD_SOURCE

The
**remainder**() function computes 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.

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.

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

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.

For an
explanation of the terms used in this section, see
**attributes**(7).

The functions
**remainder**(), **remainderf**(), and
**remainderl**() are specified in C99 and
POSIX.1-2001.

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.

The call

remainder(nan(""), 0);

returns a NaN, as expected, but wrongly causes a domain error; it should yield a silent NaN.

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

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

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