NAN(3) OpenBSD Programmer's Manual NAN(3)NAME
nan, nanf, nanl - quiet NaNs
SYNOPSIS
#include <math.h>
double
nan(const char *s);
float
nanf(const char *s);
long double
nanl(const char *s);
DESCRIPTION
The NAN macro expands to a quiet NaN (Not A Number). Similarly both the
nan(), nanf() and nanl() functions generate a quiet NaN value without
raising an invalid exception. The argument s should point to either an
empty string or a hexadecimal representation of a non-negative integer
(e.g. 0x1234). In the latter case, the integer is encoded in some free
bits in the representation of the NaN, which sometimes stores machine-
specific information about why a particular NaN was generated. There are
22 such bits available for float variables, 51 bits for double variables,
and at least 51 bits for a long double. If s is improperly formatted or
represents an integer that is too large, then the particular encoding of
the quiet NaN that is returned is indeterminate.
COMPATIBILITY
Calling these functions with a non-empty string isn't portable. Another
operating system may translate the string into a different NaN encoding,
and furthermore, the meaning of a given NaN encoding varies across
machine architectures. If you understood the innards of a particular
platform well enough to know what string to use, then you would have no
need for these functions anyway, so don't use them. Use the NAN macro
instead.
SEE ALSOisnan(3), math(3), strtod(3)STANDARDS
The nan(), nanf() and nanl() functions and the NAN macro conform to
ISO/IEC 9899:1999 (``ISO C99'').
OpenBSD 4.9 August 3, 2009 OpenBSD 4.9