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SYNOPSIS: Fixed feature test macro requirements. 

DESCRIPTION: added some details.
RETURN VALUE: Added details for special argument cases.
ERRORS: no errors can occur (previous text was misleading).
CONFORMING TO: Added POSIX.1-2001.
NOTES: point out that lrint() may be preferred in some cases.
This commit is contained in:
Michael Kerrisk 2008-08-01 05:26:39 +00:00
parent eb331ea602
commit 2517f764fe
1 changed files with 36 additions and 23 deletions
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59
man3/rint.3
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@ -1,4 +1,6 @@
.\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>.
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\" <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
@ -20,9 +22,10 @@
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.TH RINT 3 2007-07-26 "" "Linux Programmer's Manual"
.TH RINT 3 2008-07-29 "" "Linux Programmer's Manual"
.SH NAME
nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl \- round to nearest integer
nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl \- round
to nearest integer
.SH SYNOPSIS
.nf
.B #include <math.h>
@ -54,17 +57,22 @@ Feature Test Macro Requirements for glibc (see
_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
.I cc\ -std=c99
.br
.BR rint (),
.BR rint ():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
.I cc\ -std=c99
.br
.BR rintf (),
.BR rintl ():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
.I cc\ -std=c99
.ad b
.SH DESCRIPTION
The
.BR nearbyint ()
functions round their argument to an integer value in floating point
format, using the current rounding direction and without raising the
functions round their argument to an integer value in floating-point
format, using the current rounding direction (see
.BR fesetround (3))
and without raising the
.I inexact
exception.
.LP
@ -72,36 +80,41 @@ The
.BR rint ()
functions do the same, but will raise the
.I inexact
exception when the result differs in value from the argument.
exception
.RB ( FE_INEXACT ,
checkable via
.BR fetestexcept (3))
when the result differs in value from the argument.
.SH "RETURN VALUE"
The rounded integer value.
If \fIx\fP is integral or infinite,
These functions return the rounded integer value.
If \fIx\fP is integral, +0, \-0, NaN, or infinite,
\fIx\fP itself is returned.
.SH ERRORS
No errors other than
.B EDOM
and
.B ERANGE
can occur.
If \fIx\fP is NaN, then NaN is returned and
.I errno
may be set to
.BR EDOM .
No errors occur.
POSIX.1-2001 documents a "range error" for overflows, but see NOTES.
.SH "CONFORMING TO"
C99.
C99, POSIX.1-2001.
.SH NOTES
SUSv2 and POSIX.1-2001 contain text about overflow (which might set
.I errno
to
.BR ERANGE ,
or raise an exception).
or raise an
.B FE_OVERFLOW
exception).
In practice, the result cannot overflow on any current machine,
so this error-handling stuff is just nonsense.
(More precisely, overflow can happen only when the maximum value
of the exponent is smaller than the number of mantissa bits.
For the IEEE-754 standard 32-bit and 64-bit floating point numbers
the maximum value of the exponent is 128 (respectively, 1024), and the number
of mantissa bits is 24 (respectively, 53).)
For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
the maximum value of the exponent is 128 (respectively, 1024),
and the number of mantissa bits is 24 (respectively, 53).)
If you want to store the rounded value in an integer type,
you probably want to use one of the functions described in
.BR lrint (3)
instead.
.SH "SEE ALSO"
.BR ceil (3),
.BR floor (3),