1NAN(3)                        libc math functions                       NAN(3)
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NAME

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

9       #include <math.h>
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11       double nan(const char *tagp);
12       float nanf(const char *tagp);
13       long double nanl(const char *tagp);
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15       Compile with -std=c99; link with -lm.
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DESCRIPTION

18       These functions return a representation (determined by tagp) of a quiet
19       NaN. If the implementation does not support quiet NaNs, these functions
20       return zero.
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22       The  call  nan("char-sequence")  is  equivalent  to  strtod ("NAN(char-
23       sequence)",NULL) and similarly calls to nanf() and nanl()  are  equiva‐
24       lent to analogous calls to strtof() and strtold().
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26       The  argument  tagp is used in an unspecified manner.  On IEEE 754 sys‐
27       tems, there are many representations of NaN, and tagp selects one.   On
28       other systems it may do nothing.
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CONFORMING TO

31       C99.  See  also  IEC 559 and the appendix with recommended functions in
32       IEEE 754/IEEE 854.
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SEE ALSO

35       isnan(3), strtod(3)
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39GNU                               2002-08-10                            NAN(3)