nan(3) -- Linux man page
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);
DESCRIPTION
These functions return a representation (determined by
tagp)
of a quiet NaN. If the implementation does not support
quiet NaNs, these functions return zero.
The call
nan(char-sequence)
is equivalent to
strtod (NAN(char-sequence),NULL)
and similarly calls to
nanf
and
nanl
are equivalent to analogous calls to
strtof
and
strtold.
The argument
tagp
is used in an unspecified manner. On IEEE 754 systems, there are
many representations of NaN, and
tagp
selects one. On other systems it may do nothing.
CONFORMING TO
C99. See also IEC 559 and the appendix with
recommended functions in IEEE 754/IEEE 854.
SEE ALSO
isnan(3),
strtod(3)
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