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.\" $OpenBSD: nan.3,v 1.5 2011/07/07 01:34:52 martynas Exp $
.\"
.\" Copyright (c) 2007 David Schultz <das@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: src/lib/msun/man/nan.3,v 1.1 2007/12/16 21:19:28 das Exp $
.\"
.Dd $Mdocdate: July 7 2011 $
.Dt NAN 3
.Os
.Sh NAME
.Nm nan ,
.Nm nanf ,
.Nm nanl
.Nd quiet \*(Nas
.Sh SYNOPSIS
.In math.h
.Ft double
.Fn nan "const char *s"
.Ft float
.Fn nanf "const char *s"
.Ft long double
.Fn nanl "const char *s"
.Sh DESCRIPTION
The
.Dv NAN
macro expands to a quiet \*(Na (Not A Number).
Similarly both the
.Fn nan ,
.Fn nanf
and
.Fn nanl
functions generate a quiet \*(Na value without raising an invalid exception.
The argument
.Fa s
should point to either an empty string or a hexadecimal representation
of a non-negative integer (e.g. 0x1234).
In the latter case, the integer is encoded in some free bits in the
representation of the \*(Na, which sometimes stores
machine-specific information about why a particular \*(Na was generated.
There are 22 such bits available for
.Vt float
variables, 51 bits for
.Vt double
variables, and at least 51 bits for a
.Vt long double .
If
.Fa s
is improperly formatted or represents an integer that is too large,
then the particular encoding of the quiet \*(Na that is returned
is indeterminate.
.Sh COMPATIBILITY
Calling these functions with a non-empty string isn't portable.
Another operating system may translate the string into a different
\*(Na encoding, and furthermore, the meaning of a given \*(Na encoding
varies across machine architectures.
If you understood the innards of a particular platform well enough to
know what string to use, then you would have no need for these functions
anyway, so don't use them.
Use the
.Dv NAN
macro instead.
.Sh SEE ALSO
.Xr isnan 3 ,
.Xr strtod 3
.Sh STANDARDS
The
.Fn nan ,
.Fn nanf
and
.Fn nanl
functions and the
.Dv NAN
macro conform to
.St -isoC-99 .
|
