float       nanf( const char* arg );
	(1) 	(since C++11)
double      nan ( const char* arg );
	(2) 	(since C++11)
long double nanl( const char* arg );
	(3) 	(since C++11)

floatn nan(uintn nancode)
float nan(uint nancode)
doublen nan(ulongn nancode)
double nan(ulong nancode)