std::numeric_limits (3) Linux Manual Page
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
[static]
is_signed identifies signed types
[static]
is_integer identifies integer types
[static]
is_exact identifies exact types
[static]
has_infinity identifies floating-point types that can represent the special value "positive infinity"
[static]
has_quiet_NaN identifies floating-point types that can represent the special value "quiet not-a-number" (NaN)
[static]
has_signaling_NaN identifies floating-point types that can represent the special value "signaling not-a-number" (NaN)
[static]
has_denorm identifies the denormalization style used by the floating-point type
[static]
has_denorm_loss identifies the floating-point types that detect loss of precision as denormalization loss rather than inexact result
[static]
round_style identifies the rounding style used by the type
[static]
is_iec559 identifies the IEC 559/IEEE 754 floating-point types
[static]
is_bounded identifies types that represent a finite set of values
[static]
is_modulo identifies types that handle overflows with modulo arithmetic
[static]
digits number of radix digits that can be represented without change
[static]
digits10 number of decimal digits that can be represented without change
[static]
max_digits10 number of decimal digits necessary to differentiate all values of this type
[static] (C++11)
radix the radix or integer base used by the representation of the given type
[static]
min_exponent one more than the smallest negative power of the radix that is a valid normalized floating-point value
[static]
min_exponent10 the smallest negative power of ten that is a valid normalized floating-point value
[static]
max_exponent one more than the largest integer power of the radix that is a valid finite floating-point value
[static]
max_exponent10 the largest integer power of 10 that is a valid finite floating-point value
[static]
traps identifies types which can cause arithmetic operations to trap
[static]
tinyness_before identifies floating-point types that detect tinyness before rounding
[static]
Member functions
min returns the smallest finite value of the given type
[static]
lowest returns the lowest finite value of the given type
[static] (C++11)
max returns the largest finite value of the given type
[static]
epsilon returns the difference between 1.0 and the next representable value of the given floating-point type
[static]
round_error returns the maximum rounding error of the given floating-point type
[static]
infinity returns the positive infinity value of the given floating-point type
[static]
quiet_NaN returns a quiet NaN value of the given floating-point type
[static]
signaling_NaN returns a signaling NaN value of the given floating-point type
[static]
denorm_min returns the smallest positive subnormal value of the given floating-point type
[static]
Helper classes
float_round_style (enum)
float_denorm_style (enum)
Relationship with C library macro constants
Specialization min() lowest() 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<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:
See also
* Fixed_width_integer_types
* Arithmetic_types
* C++_type_system_overview
* Type_support_(basic_types,_RTTI,_type_traits)