# drem (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*.

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

|| _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

|| /* 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

|| /* Glibc versions <= 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 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)