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SYNOPSIS: Added feature test macro requirements. 

DESCRIPTION: Enhanced.
RETURN VALUE: Added details for special argument cases.
Rewrote ERRORS section.
Updated CONFORMING TO.
NOTES: Added some details.
This commit is contained in:
Michael Kerrisk 2008-08-01 05:26:03 +00:00
parent 54b0fbfb44
commit 578d105f4a
1 changed files with 50 additions and 21 deletions
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man3/ceil.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
@ -20,7 +22,7 @@
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.TH CEIL 3 2001-05-31 "" "Linux Programmer's Manual"
.TH CEIL 3 2008-07-29 "" "Linux Programmer's Manual"
.SH NAME
ceil, ceilf, ceill \- ceiling function: smallest integral value not
less than argument
@ -36,40 +38,67 @@ less than argument
.fi
.sp
Link with \fI\-lm\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR ceilf (),
.BR ceill ():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
.I cc\ -std=c99
.ad b
.SH DESCRIPTION
These functions round \fIx\fP up to the nearest integer.
These functions return the smallest integral value that is not less than
.IR x .
For example,
.IR ceil(0.5)
is 1.0, and
.IR ceil(\-0.5)
is 0.0.
.SH "RETURN VALUE"
The rounded integer value.
If \fIx\fP is integral or infinite,
These functions return the ceiling of
.IR x .
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"
The
.BR ceil ()
function conforms to SVr4, POSIX.1-2001, 4.3BSD, C89, C99.
The other functions are from C99.
C99, POSIX.1-2001.
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.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.
.\" The POSIX.1-2001 APPLICATION USAGE SECTION discusses this point.
(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 (resp. 1024), and the number
of mantissa bits is 24 (resp. 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).)
The integral value returned by these functions may be too large
to store in an integer type
.RI ( int ,
.IR long ,
etc.).
To avoid an overflow, which will produce undefined results,
an application should perform a range check on the returned value
before assigning it to an integer type.
.SH "SEE ALSO"
.BR floor (3),
.BR lrint (3),