.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
+.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
+.\" <mtk.manpages@gmail.com>
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" 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.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
.\"
.\" References consulted:
.\" Linux libc source code
.\" (walter.harms@informatik.uni-oldenburg.de)
.\" Modified 2003-11-18, 2004-10-05 aeb
.\"
-.TH REMAINDER 3 2007-07-26 "" "Linux Programmer's Manual"
+.TH REMAINDER 3 2017-09-15 "" "Linux Programmer's Manual"
.SH NAME
drem, dremf, dreml, remainder, remainderf, remainderl \- \
floating-point remainder function
.SH SYNOPSIS
.nf
.B #include <math.h>
-.sp
+.PP
/* The C99 versions */
.BI "double remainder(double " x ", double " y );
.BI "float remainderf(float " x ", float " y );
.BI "long double remainderl(long double " x ", long double " y );
-.sp
+.PP
/* Obsolete synonyms */
.BI "double drem(double " x ", double " y );
.BI "float dremf(float " x ", float " y );
.BI "long double dreml(long double " x ", long double " y );
-.sp
+.PP
.fi
Link with \fI\-lm\fP.
-.sp
+.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
-.sp
+.PP
.ad l
-.BR remainder (),
+.BR remainder ():
+.RS 4
+_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
+ || _XOPEN_SOURCE\ >=\ 500
+.\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
+ || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.RE
+.br
.BR remainderf (),
.BR remainderl ():
-_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
-.I cc\ -std=c99
+.RS 4
+_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
+ || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.RE
.br
.BR drem (),
.BR dremf (),
.BR dreml ():
-_SVID_SOURCE || _BSD_SOURCE
+.RS 4
+/* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.RE
.ad b
.SH DESCRIPTION
-The
-.BR remainder ()
-function computes the remainder of dividing
+These
+functions compute the remainder of dividing
.I x
by
.IR y .
The return value is
-.IR x " \- " n " * " y ,
+\fIx\fP\-\fIn\fP*\fIy\fP,
where
.I n
is the value
-.IR x " / " y ,
+.IR "x\ /\ y" ,
rounded to the nearest integer.
-If this quotient is 1/2 (mod 1), it is rounded to the nearest even number
-(independent of the current rounding mode).
-If the return value is 0, it has the sign of
-.IR x .
-.LP
+If the absolute value of
+\fIx\fP\-\fIn\fP*\fIy\fP
+is 0.5,
+.I n
+is chosen to be even.
+.PP
+These functions are unaffected by the current rounding mode (see
+.BR fenv (3)).
+.PP
The
.BR drem ()
function does precisely the same thing.
-.SH "RETURN VALUE"
-The
-.BR remainder ()
-function returns the remainder, unless
+.SH RETURN VALUE
+On success, these
+functions return the floating-point remainder,
+\fIx\fP\-\fIn\fP*\fIy\fP.
+If the return value is 0, it has the sign of
+.IR x .
+.PP
+If
+.I x
+or
.I y
-is zero, when the function fails and
-.I errno
-is set.
+is a NaN, a NaN is returned.
+.PP
+If
+.I x
+is an infinity,
+and
+.I y
+is not a NaN,
+a domain error occurs, and
+a NaN is returned.
+.PP
+If
+.I y
+is zero,
+.\" FIXME . Instead, glibc gives a domain error even if x is a NaN
+and
+.I x
+is not a NaN,
+.\" Interestingly, remquo(3) does not have the same problem.
+a domain error occurs, and
+a NaN is returned.
.SH ERRORS
+See
+.BR math_error (7)
+for information on how to determine whether an error has occurred
+when calling these functions.
+.PP
+The following errors can occur:
.TP
-.B EDOM
-The denominator
-.I y
-is zero.
-.SH "CONFORMING TO"
-IEC 60559.
+Domain error: \fIx\fP is an infinity and \fIy\fP is not a NaN
+.I errno
+is set to
+.BR EDOM
+(but see BUGS).
+An invalid floating-point exception
+.RB ( FE_INVALID )
+is raised.
+.IP
+These functions do not set
+.IR errno
+for this case.
+.TP
+Domain error: \fIy\fP is zero\" [XXX see bug above] and \fIx\fP is not a NaN
+.I errno
+is set to
+.BR EDOM .
+An invalid floating-point exception
+.RB ( FE_INVALID )
+is raised.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbw26 lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR drem (),
+.BR dremf (),
+.BR dreml (),
+.br
+.BR remainder (),
+.BR remainderf (),
+.br
+.BR remainderl ()
+T} Thread safety MT-Safe
+.TE
+.SH CONFORMING TO
+.\" IEC 60559.
The functions
.BR remainder (),
.BR remainderf (),
and
.BR remainderl ()
-are from C99.
+are specified in C99, POSIX.1-2001, and POSIX.1-2008.
+.PP
The function
.BR drem ()
is from 4.3BSD.
and
.BR dreml ()
exist on some systems, such as Tru64 and glibc2.
+Avoid the use of these functions in favor of
+.BR remainder ()
+etc.
+.SH BUGS
+Before glibc 2.15,
+.\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6779
+the call
+.PP
+ remainder(nan(""), 0);
+.PP
+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.
+.PP
+Before glibc 2.15,
+.\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783
+.I errno
+was not set to
+.BR EDOM
+for the domain error that occurs when
+.I x
+is an infinity and
+.I y
+is not a NaN.
.SH EXAMPLE
The call "remainder(29.0, 3.0)" returns \-1.
-.SH "SEE ALSO"
+.SH SEE ALSO
+.BR div (3),
.BR fmod (3),
.BR remquo (3)
projects / thirdparty / man-pages.git / blobdiff