nan

nan, nanf, nanl

Defined in header <math.h>
float       nanf( const char* arg );
(since C99)
double      nan( const char* arg );
(since C99)
long double nanl( const char* arg );
(since C99)

Converts the implementation-defined character string arg into the corresponding quiet NaN value, as if by calling 登录查看完整内容