# NAME

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

# LIBRARY

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

# SYNOPSIS

``````#include <math.h>
double remainder(double x, double y);
float remainderf(float x, float y);
long double remainderl(long double x, long double y);
/* Obsolete synonyms */
[[deprecated]] double drem(double x, double y);
[[deprecated]] float dremf(float x, float y);
[[deprecated]] long double dreml(long double x, long double y);``````

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.

# EXAMPLES

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

# 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

remainder()
remainderf()
remainderl()

C11, POSIX.1-2008.

drem()
dremf()
dreml()

None.

# HISTORY

remainder()
remainderf()
remainderl()

C99, POSIX.1-2001.

drem()

4.3BSD.

dremf()
dreml()

Tru64, glibc2.

# 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.