21.2 Fundamental Datatypes

The Standard C++ Library describes a specific type by providing a specialized implementation of the numeric_limits class for the type. Static functions and static constant data members then provide information specific to the type. The Standard C++ Library includes descriptions of the fundamental datatypes given in Table 20.

Table 20 -- Fundamental datatypes of the Standard C++ Library

bool	char	int	float
	signed char	short	double
	unsigned char	long	long double
		wchar_t
		unsigned short
		unsigned int
		unsigned long

Certain implementations may also provide information on other datatypes. Whether or not an implementation is described can be discovered using the static data member field is_specialized. For example, the following is legal, and will indicate that the string datatype is not described by this mechanism.

cout << "are strings described " <<
   numeric_limits<string>::is_specialized << endl;

For datatypes that do not have a specialization, the values yielded by the functions and data fields in numeric_limits are generally zero or false.