std:: numeric_limits

The std::numeric_limits class template provides a standardized way to query various properties of arithmetic types (e.g. the largest possible value for type int is std :: numeric_limits < int > :: max ( ) ).

This information is provided via specializations of the std::numeric_limits template. The standard library makes available specializations for all arithmetic types (only lists the specializations for cv-unqualified arithmetic types):

The value of each member of a specialization of std::numeric_limits on a cv-qualified type cv T is equal to the value of the corresponding member of the specialization on the unqualified type T . For example, std :: numeric_limits < int > :: digits is equal to std :: numeric_limits < const int > :: digits .

Aliases of arithmetic types (such as std::size_t or std::streamsize ) may also be examined with the std::numeric_limits type traits.

Non-arithmetic standard types, such as std:: complex < T > or std::nullptr_t , do not have specializations.

Implementations may provide specializations of std::numeric_limits for implementation-specific types: e.g. GCC provides std::numeric_limits<__int128> . Non-standard libraries may add specializations for library-provided types, e.g. OpenEXR provides std::numeric_limits<half> for a 16-bit floating-point type.

Template parameters

Member constants

Member functions

Helper classes

Relationship with C library macro constants

Example

#include <iostream>
#include <limits>
 
int main() 
{
    std::cout << "type\t│ lowest()\t│ min()\t\t│ max()\n"
              << "bool\t│ "
              << std::numeric_limits<bool>::lowest() << "\t\t│ "
              << std::numeric_limits<bool>::min() << "\t\t│ "
              << std::numeric_limits<bool>::max() << '\n'
              << "uchar\t│ "
              << +std::numeric_limits<unsigned char>::lowest() << "\t\t│ "
              << +std::numeric_limits<unsigned char>::min() << "\t\t│ "
              << +std::numeric_limits<unsigned char>::max() << '\n'
              << "int\t│ "
              << std::numeric_limits<int>::lowest() << "\t│ "
              << std::numeric_limits<int>::min() << "\t│ "
              << std::numeric_limits<int>::max() << '\n'
              << "float\t│ "
              << std::numeric_limits<float>::lowest() << "\t│ "
              << std::numeric_limits<float>::min() << "\t│ "
              << std::numeric_limits<float>::max() << '\n'
              << "double\t│ "
              << std::numeric_limits<double>::lowest() << "\t│ "
              << std::numeric_limits<double>::min() << "\t│ "
              << std::numeric_limits<double>::max() << '\n';
}

type	│ lowest()	│ min()		│ max()
bool	│ 0		│ 0		│ 1
uchar	│ 0		│ 0		│ 255
int	│ -2147483648	│ -2147483648	│ 2147483647
float	│ -3.40282e+38	│ 1.17549e-38	│ 3.40282e+38
double	│ -1.79769e+308	│ 2.22507e-308	│ 1.79769e+308

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also

• Fixed width integer types
• Arithmetic types
• C++ type system overview
• Type support (basic types, RTTI, type traits)
• C numeric limits interface