std::numeric_limits - cppreference.com (original) (raw)

| | | | | ------------------------------------------- | | | | template< class T > class 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):

| Defined in header | | | | ---------------------------------------------------------------------- | | ------------- | | template<> class numeric_limits<bool>; | | | | template<> class numeric_limits<char>; | | | | template<> class numeric_limits<signed char>; | | | | template<> class numeric_limits<unsigned char>; | | | | template<> class numeric_limits<wchar_t>; | | | | template<> class numeric_limits<char8_t>; | | (since C++20) | | template<> class numeric_limits<char16_t>; | | (since C++11) | | template<> class numeric_limits<char32_t>; | | (since C++11) | | template<> class numeric_limits<short>; | | | | template<> class numeric_limits<unsigned short>; | | | | template<> class numeric_limits<int>; | | | | template<> class numeric_limits<unsigned int>; | | | | template<> class numeric_limits<long>; | | | | template<> class numeric_limits<unsigned long>; | | | | template<> class numeric_limits<long long>; | | (since C++11) | | template<> class numeric_limits<unsigned long long>; | | (since C++11) | | template<> class numeric_limits<float>; | | | | template<> class numeric_limits<double>; | | | | template<> class numeric_limits<long double>; | | |

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.

Contents

• 1 Template parameters
• 2 Member constants
• 3 Member functions
• 4 Helper classes
• 5 Relationship with C library macro constants
• 6 Example
• 7 Defect reports
• 8 See also

[edit] Template parameters

[edit] Member constants

[edit] Member functions

[edit] Helper classes

[edit] Relationship with C library macro constants

[edit] Example

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

Possible output:

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

[edit] Defect reports

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

[edit] See also

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