ffix

[thirdparty/man-pages.git] / man3 / round.3

.\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>.
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.TH ROUND 3  2001-05-31 "" "Linux Programmer's Manual"
.SH NAME
round, roundf, roundl \- round to nearest integer, away from zero
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double round(double " x );
.br
.BI "float roundf(float " x );
.br
.BI "long double roundl(long double " x );
.fi
.sp
Compile with \fI\-std=c99\fP; link with \fI\-lm\fP.
.SH DESCRIPTION
These functions round \fIx\fP to the nearest integer, but
round halfway cases away from zero (regardless of the current rounding
direction), instead of to the nearest even integer like
.BR rint (3).
.SH "RETURN VALUE"
The rounded integer value.
If \fIx\fP is integral 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 .
.SH "CONFORMING TO"
C99.
.SH NOTES
POSIX.1-2001 contains text about overflow (which might set
.I errno
to
.BR ERANGE ,
or raise an 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 (resp. 1024), and the number
of mantissa bits is 24 (resp. 53).)
.SH "SEE ALSO"
.BR ceil (3),
.BR floor (3),
.BR lround (3),
.BR nearbyint (3),
.BR rint (3),
.BR trunc (3)