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);
 
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
remainder():
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE;
or cc -std=c99
remainderf(), remainderl():
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE;
or cc -std=c99
drem(), dremf(), dreml():
_SVID_SOURCE || _BSD_SOURCE
[Note] Note

Link with −lm.

DESCRIPTION

The remainder() function computes the remainder of dividing x by y. The return value is xn*y, where n is the value x / y, rounded to the nearest integer. If the absolute value of xn*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, xn*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

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.

CONFORMING TO

The functions remainder(), remainderf(), and remainderl() are specified in C99 and POSIX.1-2001.

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

The call

remainder(nan(""), 0);

returns a NaN, as expected, but wrongly causes a domain error; it should yield a silent 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 3.24 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)
and Copyright 2008, Linux Foundation, written by Michael Kerrisk
    <mtk.manpagesgmail.com>

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
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Formatted or processed versions of this manual, if unaccompanied by
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References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages

Modified 1993-07-24 by Rik Faith (faithcs.unc.edu)
Modified 2002-08-10 Walter Harms
(walter.harmsinformatik.uni-oldenburg.de)
Modified 2003-11-18, 2004-10-05 aeb