nanl(3) - f39

1nan(3)                     Library Functions Manual                     nan(3)
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NAME

6       nan, nanf, nanl - return 'Not a Number'
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LIBRARY

9       Math library (libm, -lm)
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SYNOPSIS

12       #include <math.h>
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14       double nan(const char *tagp);
15       float nanf(const char *tagp);
16       long double nanl(const char *tagp);
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18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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20       nan(), nanf(), nanl():
21           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
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DESCRIPTION

24       These functions return a representation (determined by tagp) of a quiet
25       NaN.  If the implementation does not support quiet  NaNs,  these  func‐
26       tions return zero.
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28       The call nan("char-sequence") is equivalent to:
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30           strtod("NAN(char-sequence)", NULL);
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32       Similarly, calls to nanf() and nanl() are equivalent to analogous calls
33       to strtof(3) and strtold(3).
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35       The argument tagp is used in an unspecified manner.  On IEEE  754  sys‐
36       tems,  there are many representations of NaN, and tagp selects one.  On
37       other systems it may do nothing.
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ATTRIBUTES

40       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
41       tributes(7).
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43       ┌─────────────────────────────────────┬───────────────┬────────────────┐
44       │Interface                            │ Attribute     │ Value          │
45       ├─────────────────────────────────────┼───────────────┼────────────────┤
46       │nan(), nanf(), nanl()                │ Thread safety │ MT-Safe locale │
47       └─────────────────────────────────────┴───────────────┴────────────────┘
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STANDARDS

50       C11, POSIX.1-2008.
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52       See  also  IEC  559 and the appendix with recommended functions in IEEE
53       754/IEEE 854.
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HISTORY

56       glibc 2.1.  C99, POSIX.1-2001.
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