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