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man:nanl

NAN(3) Linux Programmer's Manual NAN(3)

NAME

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

SYNOPSIS

     #include <math.h>
     double nan(const char *tagp);
     float nanf(const char *tagp);
     long double nanl(const char *tagp);
     Link with -lm.
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
     nan(), nanf(), nanl():
         _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION

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

VERSIONS

     These functions first appeared in glibc in version 2.1.

ATTRIBUTES

     For  an  explanation  of  the  terms  used   in   this   section,   see
     attributes(7).
     allbox; lbw21 lb lb l l l.  Interface Attribute Value T{ nan(), nanf(),
     nanl() T}   Thread safety  MT-Safe locale

CONFORMING TO

     C99, POSIX.1-2001, POSIX.1-2008.  See also IEC  559  and  the  appendix
     with recommended functions in IEEE 754/IEEE 854.

SEE ALSO

     isnan(3), strtod(3), math_error(7)

COLOPHON

     This  page  is  part of release 4.16 of the Linux man-pages project.  A
     description of the project, information about reporting bugs,  and  the
     latest     version     of     this    page,    can    be    found    at
     https://www.kernel.org/doc/man-pages/.

GNU 2016-03-15 NAN(3)

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