1.\" $OpenBSD: nan.3,v 1.5 2011/07/07 01:34:52 martynas Exp $ 2.\" 3.\" Copyright (c) 2007 David Schultz <das@FreeBSD.org> 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.\" $FreeBSD: src/lib/msun/man/nan.3,v 1.1 2007/12/16 21:19:28 das Exp $ 28.\" 29.Dd $Mdocdate: July 7 2011 $ 30.Dt NAN 3 31.Os 32.Sh NAME 33.Nm nan , 34.Nm nanf , 35.Nm nanl 36.Nd quiet \*(Nas 37.Sh SYNOPSIS 38.In math.h 39.Ft double 40.Fn nan "const char *s" 41.Ft float 42.Fn nanf "const char *s" 43.Ft long double 44.Fn nanl "const char *s" 45.Sh DESCRIPTION 46The 47.Dv NAN 48macro expands to a quiet \*(Na (Not A Number). 49Similarly both the 50.Fn nan , 51.Fn nanf 52and 53.Fn nanl 54functions generate a quiet \*(Na value without raising an invalid exception. 55The argument 56.Fa s 57should point to either an empty string or a hexadecimal representation 58of a non-negative integer (e.g. 0x1234). 59In the latter case, the integer is encoded in some free bits in the 60representation of the \*(Na, which sometimes stores 61machine-specific information about why a particular \*(Na was generated. 62There are 22 such bits available for 63.Vt float 64variables, 51 bits for 65.Vt double 66variables, and at least 51 bits for a 67.Vt long double . 68If 69.Fa s 70is improperly formatted or represents an integer that is too large, 71then the particular encoding of the quiet \*(Na that is returned 72is indeterminate. 73.Sh COMPATIBILITY 74Calling these functions with a non-empty string isn't portable. 75Another operating system may translate the string into a different 76\*(Na encoding, and furthermore, the meaning of a given \*(Na encoding 77varies across machine architectures. 78If you understood the innards of a particular platform well enough to 79know what string to use, then you would have no need for these functions 80anyway, so don't use them. 81Use the 82.Dv NAN 83macro instead. 84.Sh SEE ALSO 85.Xr isnan 3 , 86.Xr strtod 3 87.Sh STANDARDS 88The 89.Fn nan , 90.Fn nanf 91and 92.Fn nanl 93functions and the 94.Dv NAN 95macro conform to 96.St -isoC-99 . 97