# remainder

```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 in-
teger.  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 at-
tributes(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.

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

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

COLOPHON
This  page  is  part of release 5.05 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                      REMAINDER(3)```