std::numeric_limits (3) - Linux Manuals

std::numeric_limits: std::numeric_limits

NAME

std::numeric_limits - std::numeric_limits

Synopsis

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<char8_t>; // C++20 feature
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.

Template parameters

T - a type to retrieve numeric properties for

Member constants

is_specialized identifies types for which std::numeric_limits is specialized
                  (public static member constant)
[static]

is_signed identifies signed types
                  (public static member constant)
[static]

is_integer identifies integer types
                  (public static member constant)
[static]

is_exact identifies exact types
                  (public static member constant)
[static]

has_infinity identifies floating-point types that can represent the special value "positive infinity"
                  (public static member constant)
[static]

has_quiet_NaN identifies floating-point types that can represent the special value "quiet not-a-number" (NaN)
                  (public static member constant)
[static]

has_signaling_NaN identifies floating-point types that can represent the special value "signaling not-a-number" (NaN)
                  (public static member constant)
[static]

has_denorm identifies the denormalization style used by the floating-point type
                  (public static member constant)
[static]

has_denorm_loss identifies the floating-point types that detect loss of precision as denormalization loss rather than inexact result
                  (public static member constant)
[static]

round_style identifies the rounding style used by the type
                  (public static member constant)
[static]

is_iec559 identifies the IEC 559/IEEE 754 floating-point types
                  (public static member constant)
[static]

is_bounded identifies types that represent a finite set of values
                  (public static member constant)
[static]

is_modulo identifies types that handle overflows with modulo arithmetic
                  (public static member constant)
[static]

digits number of radix digits that can be represented without change
                  (public static member constant)
[static]

digits10 number of decimal digits that can be represented without change
                  (public static member constant)
[static]

max_digits10 number of decimal digits necessary to differentiate all values of this type
                  (public static member constant)
[static] (C++11)

radix the radix or integer base used by the representation of the given type
                  (public static member constant)
[static]

min_exponent one more than the smallest negative power of the radix that is a valid normalized floating-point value
                  (public static member constant)
[static]

min_exponent10 the smallest negative power of ten that is a valid normalized floating-point value
                  (public static member constant)
[static]

max_exponent one more than the largest integer power of the radix that is a valid finite floating-point value
                  (public static member constant)
[static]

max_exponent10 the largest integer power of 10 that is a valid finite floating-point value
                  (public static member constant)
[static]

traps identifies types which can cause arithmetic operations to trap
                  (public static member constant)
[static]

tinyness_before identifies floating-point types that detect tinyness before rounding
                  (public static member constant)
[static]

Member functions

min returns the smallest finite value of the given type
                 (public static member function)
[static]

lowest returns the lowest finite value of the given type
                 (public static member function)
[static] (C++11)

max returns the largest finite value of the given type
                 (public static member function)
[static]

epsilon returns the difference between 1.0 and the next representable value of the given floating-point type
                 (public static member function)
[static]

round_error returns the maximum rounding error of the given floating-point type
                 (public static member function)
[static]

infinity returns the positive infinity value of the given floating-point type
                 (public static member function)
[static]

quiet_NaN returns a quiet NaN value of the given floating-point type
                 (public static member function)
[static]

signaling_NaN returns a signaling NaN value of the given floating-point type
                 (public static member function)
[static]

denorm_min returns the smallest positive subnormal value of the given floating-point type
                 (public static member function)
[static]

Helper classes

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

Relationship with C library macro constants

                                   Members
Specialization min() lowest() max() epsilon() digits digits10 min_exponent min_exponent10 max_exponent max_exponent10 radix
                                             (C++11)
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<char8_t> 0 0 UCHAR_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

Example

// Run this code

  #include <limits>
  #include <iostream>

  int main()
  {
      std::cout << "type\tlowest()\tmin()\t\tmax()\n\n";

      std::cout << "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';
      std::cout << "int\t"
                << std::numeric_limits<int>::lowest() << '\t'
                << std::numeric_limits<int>::min() << '\t'
                << std::numeric_limits<int>::max() << '\n';
      std::cout << "float\t"
                << std::numeric_limits<float>::lowest() << '\t'
                << std::numeric_limits<float>::min() << '\t'
                << std::numeric_limits<float>::max() << '\n';
      std::cout << "double\t"
                << std::numeric_limits<double>::lowest() << '\t'
                << std::numeric_limits<double>::min() << '\t'
                << std::numeric_limits<double>::max() << '\n';
  }

Possible output:

  type lowest() min() max()

  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