man3/nan.3

   1 .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\"
   3 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
   4 .\" Distributed under GPL
   5 .\" %%%LICENSE_END
   6 .\"
   7 .\" Based on glibc infopages
   8 .\"
   9 .\" Corrections by aeb
  10 .\"
  11 .TH NAN 3 2016-03-15 "GNU" "Linux Programmer's Manual"
  12 .SH NAME
  13 nan, nanf, nanl \- return 'Not a Number'
  14 .SH SYNOPSIS
  15 .B #include <math.h>
  16 .PP
  17 .BI "double nan(const char *" tagp );
  18 .br
  19 .BI "float nanf(const char *" tagp );
  20 .br
  21 .BI "long double nanl(const char *" tagp );
  22 .PP
  23 Link with \fI\-lm\fP.
  24 .PP
  25 .in -4n
  26 Feature Test Macro Requirements for glibc (see
  27 .BR feature_test_macros (7)):
  28 .in
  29 .PP
  30 .ad l
  31 .BR nan (),
  32 .BR nanf (),
  33 .BR nanl ():
  34 .RS 4
  35 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  36 .RE
  37 .ad
  38 .SH DESCRIPTION
  39 These functions return a representation (determined by
  40 .IR tagp )
  41 of a quiet NaN.
  42 If the implementation does not support
  43 quiet NaNs, these functions return zero.
  44 .PP
  45 The call
  46 .I nan("char-sequence")
  47 is equivalent to:
  48 .PP
  49 .in +4n
  50 .EX
  51 strtod("NAN(char-sequence)", NULL);
  52 .EE
  53 .in
  54 .PP
  55 Similarly, calls to
  56 .BR nanf ()
  57 and
  58 .BR nanl ()
  59 are equivalent to analogous calls to
  60 .BR strtof (3)
  61 and
  62 .BR strtold (3).
  63 .PP
  64 The argument
  65 .I tagp
  66 is used in an unspecified manner.
  67 On IEEE 754 systems, there are many representations of NaN, and
  68 .I tagp
  69 selects one.
  70 On other systems it may do nothing.
  71 .SH VERSIONS
  72 These functions first appeared in glibc in version 2.1.
  73 .SH ATTRIBUTES
  74 For an explanation of the terms used in this section, see
  75 .BR attributes (7).
  76 .TS
  77 allbox;
  78 lbw21 lb lb
  79 l l l.
  80 Interface       Attribute       Value
  81 T{
  82 .BR nan (),
  83 .BR nanf (),
  84 .BR nanl ()
  85 T}      Thread safety   MT-Safe locale
  86 .TE
  87 .SH CONFORMING TO
  88 C99, POSIX.1-2001, POSIX.1-2008.
  89 See also IEC 559 and the appendix with
  90 recommended functions in IEEE 754/IEEE 854.
  91 .SH SEE ALSO
  92 .BR isnan (3),
  93 .BR strtod (3),
  94 .BR math_error (7)