NAN(3) Library Functions Manual NAN(3)

nan, nanf, nanl
return quiet NaN

Math Library (libm, -lm)

#include <math.h>

double
nan(const char *tagp);

float
nanf(const char *tagp);

long double
nanl(const char *tagp);

The call nan("n-char-sequence") is equivalent to the call strtod("NAN(n-char-sequence)", NULL). The call nan("") is equivalent to the call strtod("NAN()", NULL).

The nanf() and nanl() functions are equivalent to nan() but substituting strtof() and strtold(), respectively.

The nan(), nanf(), and nanl() functions return a quiet NaN as specified by tagp.

The nan(), nanf(), and nanl() functions return zero.

math(3), strtod(3)

The nan(), nanf(), and nanl() functions conform to ISO/IEC 9899:1999 (“ISO C99”).
March 15, 2006 NetBSD 9.2