1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
3 .\" <mtk.manpages@gmail.com>
5 .\" %%%LICENSE_START(VERBATIM)
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10 .\" Permission is granted to copy and distribute modified versions of this
11 .\" manual under the conditions for verbatim copying, provided that the
12 .\" entire resulting derived work is distributed under the terms of a
13 .\" permission notice identical to this one.
15 .\" Since the Linux kernel and libraries are constantly changing, this
16 .\" manual page may be incorrect or out-of-date. The author(s) assume no
17 .\" responsibility for errors or omissions, or for damages resulting from
18 .\" the use of the information contained herein. The author(s) may not
19 .\" have taken the same level of care in the production of this manual,
20 .\" which is licensed free of charge, as they might when working
23 .\" Formatted or processed versions of this manual, if unaccompanied by
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27 .\" References consulted:
28 .\" Linux libc source code
29 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
32 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
33 .\" Modified 2002-08-10 Walter Harms
34 .\" (walter.harms@informatik.uni-oldenburg.de)
35 .\" Modified 2003-11-18, 2004-10-05 aeb
37 .TH REMAINDER 3 2010-09-20 "" "Linux Programmer's Manual"
39 drem, dremf, dreml, remainder, remainderf, remainderl \- \
40 floating-point remainder function
45 /* The C99 versions */
46 .BI "double remainder(double " x ", double " y );
47 .BI "float remainderf(float " x ", float " y );
48 .BI "long double remainderl(long double " x ", long double " y );
50 /* Obsolete synonyms */
51 .BI "double drem(double " x ", double " y );
52 .BI "float dremf(float " x ", float " y );
53 .BI "long double dreml(long double " x ", long double " y );
59 Feature Test Macro Requirements for glibc (see
60 .BR feature_test_macros (7)):
66 _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
67 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED ||
69 _POSIX_C_SOURCE\ >=\ 200112L;
78 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
79 _POSIX_C_SOURCE\ >=\ 200112L;
89 _SVID_SOURCE || _BSD_SOURCE
95 function computes the remainder of dividing
100 \fIx\fP\-\fIn\fP*\fIy\fP,
105 rounded to the nearest integer.
106 If the absolute value of
107 \fIx\fP\-\fIn\fP*\fIy\fP
110 is chosen to be even.
112 These functions are unaffected by the current rounding mode (see
117 function does precisely the same thing.
120 functions return the floating-point remainder,
121 \fIx\fP\-\fIn\fP*\fIy\fP.
122 If the return value is 0, it has the sign of
129 is a NaN, a NaN is returned.
137 a domain error occurs, and
143 .\" FIXME . Instead, glibc gives a domain error even if x is a NaN
147 .\" Interestingly, remquo(3) does not have the same problem.
148 a domain error occurs, and
153 for information on how to determine whether an error has occurred
154 when calling these functions.
156 The following errors can occur:
158 Domain error: \fIx\fP is an infinity and \fIy\fP is not a NaN
162 An invalid floating-point exception
166 These functions do not set
169 .\" FIXME . Is it intentional that these functions do not set errno?
170 .\" They do set errno for the y == 0 case, below.
171 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783
173 Domain error: \fIy\fP is zero\" [XXX see bug above] and \fIx\fP is not a NaN
177 An invalid floating-point exception
187 are specified in C99 and POSIX.1-2001.
200 exist on some systems, such as Tru64 and glibc2.
201 Avoid the use of these functions in favor of
207 remainder(nan(""), 0);
209 returns a NaN, as expected, but wrongly causes a domain error;
210 it should yield a silent NaN.
211 .\" FIXME . this bug occurs as at glibc 2.8.
212 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6779
214 The call "remainder(29.0, 3.0)" returns \-1.