std::numeric_limits
| Defined in header  <limits> | ||
| template< class T > class numeric_limits; | ||
The numeric_limits class template provides a standardized way to query various properties of fundamental 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 fundamental types:
| Defined in header  <limits> | ||
| template<> class numeric_limits<bool>; template<> class numeric_limits<char>; | ||
Additionally, a specialization exists for every cv-qualified version of each fundamental 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 fundamental types (such as std::size_t or std::streamsize may also be examined with the std::numeric_limits type traits.
Implementations may provide specializations of std::numeric_limits for implementation-specific types: e.g. GCC provides std::numeric_limits<__int128>. 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 radixdigits 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 1.0and 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
#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


