mirror of https://github.com/mkerrisk/man-pages
SYNOPSIS: Fixed feature test macro requirements.
DESCRIPTION: added some details. RETURN VALUE: Added details for special argument cases. Rewrote ERRORS section; noted that errno is not always set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783. Updated CONFORMING TO. Added BUGS section noting that remainder(nan(""), 0) wrongly causes a domain error; see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6779
This commit is contained in:
Michael Kerrisk
parent
207ce83e6f
commit
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105
man3/remainder.3
105
man3/remainder.3
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@ -1,4 +1,6 @@
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.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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@ -30,7 +32,7 @@
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.\" (walter.harms@informatik.uni-oldenburg.de)
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.\" Modified 2003-11-18, 2004-10-05 aeb
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.\"
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.TH REMAINDER 3 2008-06-16 "" "Linux Programmer's Manual"
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.TH REMAINDER 3 2008-07-29 "" "Linux Programmer's Manual"
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.SH NAME
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drem, dremf, dreml, remainder, remainderf, remainderl \- \
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floating-point remainder function
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@ -57,10 +59,13 @@ Feature Test Macro Requirements for glibc (see
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.in
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.sp
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.ad l
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.BR remainder (),
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.BR remainder ():
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_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.br
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.BR remainderf (),
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.BR remainderl ():
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_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
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_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.br
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.BR drem (),
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@ -76,42 +81,93 @@ function computes the remainder of dividing
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by
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.IR y .
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The return value is
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.IR "x\ \-\ n\ *\ y" ,
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\fIx\fP\-\fIn\fP*\fIy\fP,
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where
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.I n
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is the value
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.IR "x\ /\ y" ,
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rounded to the nearest integer.
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If this quotient is 1/2 (mod 1), it is rounded to the nearest even number
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(independent of the current rounding mode).
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If the return value is 0, it has the sign of
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.IR x .
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If the absolute value of
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\fIx\fP\-\fIn\fP*\fIy\fP
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is 0.5,
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.I n
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is chosen to be even.
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These functions are unaffected by the current rounding mode.
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.LP
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The
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.BR drem ()
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function does precisely the same thing.
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.SH "RETURN VALUE"
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The
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.BR remainder ()
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function returns the remainder, unless
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On success, these
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functions return the floating-point remainder,
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\fIx\fP\-\fIn\fP*\fIy\fP.
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If the return value is 0, it has the sign of
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.IR x .
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If
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.I x
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or
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.I y
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is zero, when the function fails and
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.I errno
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is set.
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is a NaN, a NaN is returned.
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If
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.I x
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is an infinity,
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and
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.I y
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is not a NaN,
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a "domain error" occurs, and
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a NaN is returned.
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If
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.I y
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is zero,
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.\" FIXME . Instead, glibc gives a domain error even if x is a NaN
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and
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.I x
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is not a NaN,
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.\" Interestingly, remquo(3) does not have the same problem.
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a "domain error" occurs, and
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a NaN is returned.
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.SH ERRORS
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See
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.BR math_error (7)
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for information on how to determine whether an error has occurred
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when calling these functions.
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.PP
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The following errors can occur:
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.TP
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.B EDOM
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The denominator
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.I y
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is zero.
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Domain error: \fIx\fP is an infinity and \fIy\fP is not a NaN
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.\" .I errno
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.\" is set to
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.\" .BR EDOM .
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An invalid floating-point exception
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.RB ( FE_INVALID )
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is raised.
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.IP
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These functions do not set
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.IR errno
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for this case.
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.\" FIXME . Is it intentional that these functions do not set errno?
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.\" They do set errno for the y == 0 case, below.
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.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783
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.TP
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Domain error: \fIy\fP is zero\" [XXX see bug above] and \fIx\fP is not a NaN
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.I errno
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is set to
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.BR EDOM .
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An invalid floating-point exception
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.RB ( FE_INVALID )
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is raised.
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.SH "CONFORMING TO"
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IEC 60559.
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.\" IEC 60559.
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The functions
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.BR remainder (),
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.BR remainderf (),
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and
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.BR remainderl ()
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are from C99.
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are specified in C99 and POSIX.1-2001.
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The function
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.BR drem ()
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@ -130,6 +186,15 @@ Avoid the use of these functions in favor of
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etc.
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.SH EXAMPLE
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The call "remainder(29.0, 3.0)" returns \-1.
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.SH BUGS
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The call
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remainder(nan(""), 0);
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returns a NaN, as expected, but wrongly causes a domain error;
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it should yield a silent NaN.
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.\" FIXME . this bug occurs as at glibc 2.8.
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.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6779
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.SH "SEE ALSO"
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.BR fmod (3),
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.BR remquo (3)
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