std::numeric_limits

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C numeric limits interface
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std::numeric_limits
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Defined in header <limits>
template< class T > class numeric_limits;

The 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 numeric_limits template. The standard library makes available specializations for all arithmetic types:

Defined in header <limits>
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<char16_t>;   // C++11 feature
template<> class numeric_limits<char32_t>;   // C++11 feature
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>;
template<> class numeric_limits<unsigned long long>;
template<> class numeric_limits<float>;
template<> class numeric_limits<double>;

template<> class numeric_limits<long double>;

Additionally, a specialization exists for every cv-qualified version of each arithmetic type, identical to the unqualified specialization, e.g. std::numeric_limits<const int>, std::numeric_limits<volatile int>, and std::numeric_limits<const volatile int> are provided and are equivalent to std::numeric_limits<int>.

The standard library types that are 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

[edit] Template parameters

T - a type to retrieve numeric properties for

[edit] Member constants

[static]
 identifies types for which std::numeric_limits is specialized
(public static member constant)
[static]
 identifies signed types
(public static member constant)
[static]
 identifies integer types
(public static member constant)
[static]
 identifies exact types
(public static member constant)
[static]
 identifies floating-point types that can represent the special value "positive infinity"
(public static member constant)
[static]
 identifies floating-point types that can represent the special value "quiet not-a-number" (NaN)
(public static member constant)
[static]
 identifies floating-point types that can represent the special value "signaling not-a-number" (NaN)
(public static member constant)
[static]
 identifies the denormalization style used by the floating-point type
(public static member constant)
[static]
 identifies the floating-point types that detect loss of precision as denormalization loss rather than inexact result
(public static member constant)
[static]
 identifies the rounding style used by the type
(public static member constant)
[static]
 identifies the IEC 559/IEEE 754 floating-point types
(public static member constant)
[static]
 identifies types that represent a finite set of values
(public static member constant)
[static]
 identifies types that handle overflows with modulo arithmetic
(public static member constant)
[static]
 number of radix digits that can be represented without change
(public static member constant)
[static]
 number of decimal digits that can be represented without change
(public static member constant)
[static] (C++11)
 number of decimal digits necessary to differentiate all values of this type
(public static member constant)
[static]
 the radix or integer base used by the representation of the given type
(public static member constant)
[static]
 one more than the smallest negative power of the radix that is a valid normalized floating-point value
(public static member constant)
[static]
 the smallest negative power of ten that is a valid normalized floating-point value
(public static member constant)
[static]
 one more than the largest integer power of the radix that is a valid finite floating-point value
(public static member constant)
[static]
 the largest integer power of 10 that is a valid finite floating-point value
(public static member constant)
[static]
 identifies types which can cause arithmetic operations to trap
(public static member constant)
[static]
 identifies floating-point types that detect tinyness before rounding
(public static member constant)

[edit] Member functions

[static]
 returns the smallest finite value of the given type
(public static member function)
[static] (C++11)
 returns the lowest finite value of the given type
(public static member function)
[static]
 returns the largest finite value of the given type
(public static member function)
[static]
 returns the difference between 1.0 and the next representable value of the given floating-point type
(public static member function)
[static]
 returns the maximum rounding error of the given floating-point type
(public static member function)
[static]
 returns the positive infinity value of the given floating-point type
(public static member function)
[static]
 returns a quiet NaN value of the given floating-point type
(public static member function)
[static]
 returns a signaling NaN value of the given floating-point type
(public static member function)
[static]
 returns the smallest positive subnormal value of the given floating-point type
(public static member function)

[edit] Helper classes

indicates floating-point rounding modes
(enum)
indicates floating-point denormalization modes
(enum)

[edit] Relationship with C library macro constants

Specialization Members
min() lowest()
(C++11) 		max() epsilon() digits digits10 min_exponent min_exponent10 max_exponent max_exponent10 radix
numeric_limits< bool > 2
numeric_limits< char > CHAR_MIN CHAR_MIN CHAR_MAX 2
numeric_limits< signed char > SCHAR_MIN SCHAR_MIN SCHAR_MAX 2
numeric_limits< unsigned char > ​0​ ​0​ UCHAR_MAX 2
numeric_limits< wchar_t > WCHAR_MIN WCHAR_MIN WCHAR_MAX 2
numeric_limits< char16_t > ​0​ ​0​ UINT_LEAST16_MAX 2
numeric_limits< char32_t > ​0​ ​0​ UINT_LEAST32_MAX 2
numeric_limits< short > SHRT_MIN SHRT_MIN SHRT_MAX 2
numeric_limits< signed short >
numeric_limits< unsigned short > ​0​ ​0​ USHRT_MAX 2
numeric_limits< int > INT_MIN INT_MIN INT_MAX 2
numeric_limits< signed int >
numeric_limits< unsigned int > ​0​ ​0​ UINT_MAX 2
numeric_limits< long > LONG_MIN LONG_MIN LONG_MAX 2
numeric_limits< signed long >
numeric_limits< unsigned long > ​0​ ​0​ ULONG_MAX 2
numeric_limits< long long > LLONG_MIN LLONG_MIN LLONG_MAX 2
numeric_limits< signed long long >
numeric_limits< unsigned long long > ​0​ ​0​ ULLONG_MAX 2
numeric_limits< float > FLT_MIN -FLT_MAX FLT_MAX FLT_EPSILON FLT_MANT_DIG FLT_DIG FLT_MIN_EXP FLT_MIN_10_EXP FLT_MAX_EXP FLT_MAX_10_EXP FLT_RADIX
numeric_limits< double > DBL_MIN -DBL_MAX DBL_MAX DBL_EPSILON DBL_MANT_DIG DBL_DIG DBL_MIN_EXP DBL_MIN_10_EXP DBL_MAX_EXP DBL_MAX_10_EXP FLT_RADIX
numeric_limits< long double > LDBL_MIN -LDBL_MAX LDBL_MAX LDBL_EPSILON LDBL_MANT_DIG LDBL_DIG LDBL_MIN_EXP LDBL_MIN_10_EXP LDBL_MAX_EXP LDBL_MAX_10_EXP FLT_RADIX

[edit] Example

Run this code
#include <limits>
#include <iostream>
 
int main() 
{
    std::cout << "type\tlowest\thighest\n";
    std::cout << "int\t"
              << std::numeric_limits<int>::lowest() << '\t'
              << std::numeric_limits<int>::max() << '\n';
    std::cout << "float\t"
              << std::numeric_limits<float>::lowest() << '\t'
              << std::numeric_limits<float>::max() << '\n';
    std::cout << "double\t"
              << std::numeric_limits<double>::lowest() << '\t'
              << std::numeric_limits<double>::max() << '\n';
}

Possible output: 

type    lowest         highest
int     -2147483648    2147483647
float   -3.40282e+38   3.40282e+38
double  -1.79769e+308  1.79769e+308

[edit] See also

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