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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 */Link withdouble drem(doublex, doubley);float dremf(floatx, floaty);long double dreml(long doublex, long doubley);

*-lm*.

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

**remainder**():

**remainderf**(),

**remainderl**():

**drem**(),

**dremf**(),

**dreml**():

# 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 callremainder(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.

# EXAMPLE¶

The call "remainder(29.0, 3.0)" returns -1.# SEE ALSO¶

div(3), fmod(3), remquo(3)# COLOPHON¶

This page is part of release 5.02 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/.

2017-09-15 |