# dremf

```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(double x, double y);
float remainderf(float x, float y);
long double remainderl(long double x, long double y);

/* Obsolete synonyms */
double drem(double x, double y);
float dremf(float x, float y);
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 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
drem(), dremf(), dreml():
/* Since glibc 2.19: */ _DEFAULT_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(),  | Thread safety | MT-Safe |
|remainder(), remainderf(), |               |         |
|remainderl()               |               |         |
+---------------------------+---------------+---------+
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.  errno was not set

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