NAN(3) Library Functions Manual NAN(3)
NAME
nan, nanf, nanlreturn quiet NaN
LIBRARY
Math Library (libm, -lm)
SYNOPSIS
#include <math.h>
double
nan(const char *tagp);
float
nanf(const char *tagp);
long double
nanl(const char *tagp);
DESCRIPTION
The call nan("n-char-sequence") is equivalent to the call strod("NAN(n-char-sequence)", NULL). The call nan("") is equivalent to the call strod("NAN()", NULL).
 
The nanf() and nanl() functions are equivalent to nan() but substituting strtof() and strtod(), respectively.
RETURN VALUES
IEEE 754
The nan(), nanf(), and nanl() functions return a quiet NaN as specified by tagp.
VAX
The nan(), nanf(), and nanl() functions return zero.
SEE ALSO
STANDARDS
The nan(), nanf(), and nanl() functions conform to ISO/IEC 9899:1999 (“ISO C99”).