std::numeric_limits

 

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ptrdiff_t size_t max_align_t (C++11)     byte (C++17)	nullptr_t (C++11) offsetof NULL
Numeric limits
numeric_limits
C numeric limits interface
Runtime type information
type_info type_index (C++11)	bad_typeid bad_cast

 

std::numeric_limits

Static constants

numeric_limits::is_specialized

numeric_limits::is_signed

numeric_limits::is_integer

numeric_limits::is_exact

numeric_limits::has_infinity

numeric_limits::has_quiet_NaN

numeric_limits::has_signaling_NaN

numeric_limits::has_denorm

numeric_limits::has_denorm_loss

numeric_limits::round_style

numeric_limits::is_iec559

numeric_limits::is_bounded

numeric_limits::is_modulo

numeric_limits::digits

numeric_limits::digits10

numeric_limits::max_digits10 (C++11)

numeric_limits::radix

numeric_limits::min_exponent

numeric_limits::min_exponent10

numeric_limits::max_exponent

numeric_limits::max_exponent10

numeric_limits::traps

numeric_limits::tinyness_before

Static member functions

numeric_limits::min

numeric_limits::lowest (C++11)

numeric_limits::max

numeric_limits::epsilon

numeric_limits::round_error

numeric_limits::infinity

numeric_limits::quiet_NaN

numeric_limits::signaling_NaN

numeric_limits::denorm_min

Helper types

float_round_style

float_denorm_style

 

Defined in header <limits>
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 <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>;		(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.

If the implementation defines any integer-class types, specializations of std::numeric_limits must also be provided for them.

(since C++20)

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 [static]	identifies types for which std::numeric_limits is specialized (public static member constant)
is_signed [static]	identifies signed types (public static member constant)
is_integer [static]	identifies integer types (public static member constant)
is_exact [static]	identifies exact types (public static member constant)
has_infinity [static]	identifies floating-point types that can represent the special value "positive infinity" (public static member constant)
has_quiet_NaN [static]	identifies floating-point types that can represent the special value "quiet not-a-number" (NaN) (public static member constant)
has_signaling_NaN [static]	identifies floating-point types that can represent the special value "signaling not-a-number" (NaN) (public static member constant)
has_denorm [static]	identifies the denormalization style used by the floating-point type (public static member constant)
has_denorm_loss [static]	identifies the floating-point types that detect loss of precision as denormalization loss rather than inexact result (public static member constant)
round_style [static]	identifies the rounding style used by the type (public static member constant)
is_iec559 [static]	identifies the IEC 559/IEEE 754 floating-point types (public static member constant)
is_bounded [static]	identifies types that represent a finite set of values (public static member constant)
is_modulo [static]	identifies types that handle overflows with modulo arithmetic (public static member constant)
digits [static]	number of radix digits that can be represented without change (public static member constant)
digits10 [static]	number of decimal digits that can be represented without change (public static member constant)
max_digits10 [static] (C++11)	number of decimal digits necessary to differentiate all values of this type (public static member constant)
radix [static]	the radix or integer base used by the representation of the given type (public static member constant)
min_exponent [static]	one more than the smallest negative power of the radix that is a valid normalized floating-point value (public static member constant)
min_exponent10 [static]	the smallest negative power of ten that is a valid normalized floating-point value (public static member constant)
max_exponent [static]	one more than the largest integer power of the radix that is a valid finite floating-point value (public static member constant)
max_exponent10 [static]	the largest integer power of 10 that is a valid finite floating-point value (public static member constant)
traps [static]	identifies types which can cause arithmetic operations to trap (public static member constant)
tinyness_before [static]	identifies floating-point types that detect tinyness before rounding (public static member constant)

Member functions

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

Helper classes

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

Relationship with C library macro constants

Specialization std::numeric_limits<T> where T is	Members
	min()	lowest() (C++11)	max()	radix
bool	false	false	true	2
char	CHAR_MIN	CHAR_MIN	CHAR_MAX	2
signed char	SCHAR_MIN	SCHAR_MIN	SCHAR_MAX	2
unsigned char	​0​	​0​	UCHAR_MAX	2
wchar_t	WCHAR_MIN	WCHAR_MIN	WCHAR_MAX	2
char8_t	​0​	​0​	UCHAR_MAX	2
char16_t	​0​	​0​	UINT_LEAST16_MAX	2
char32_t	​0​	​0​	UINT_LEAST32_MAX	2
short	SHRT_MIN	SHRT_MIN	SHRT_MAX	2
signed short
unsigned short	​0​	​0​	USHRT_MAX	2
int	INT_MIN	INT_MIN	INT_MAX	2
signed int
unsigned int	​0​	​0​	UINT_MAX	2
long	LONG_MIN	LONG_MIN	LONG_MAX	2
signed long
unsigned long	​0​	​0​	ULONG_MAX	2
long long	LLONG_MIN	LLONG_MIN	LLONG_MAX	2
signed long long
unsigned long long	​0​	​0​	ULLONG_MAX	2

Specialization std::numeric_limits<T> where T is	Members
	denorm_min()	min()	lowest() (C++11)	max()	epsilon()	digits	digits10
float	FLT_TRUE_MIN	FLT_MIN	-FLT_MAX	FLT_MAX	FLT_EPSILON	FLT_MANT_DIG	FLT_DIG
double	DBL_TRUE_MIN	DBL_MIN	-DBL_MAX	DBL_MAX	DBL_EPSILON	DBL_MANT_DIG	DBL_DIG
long double	LDBL_TRUE_MIN	LDBL_MIN	-LDBL_MAX	LDBL_MAX	LDBL_EPSILON	LDBL_MANT_DIG	LDBL_DIG

Specialization std::numeric_limits<T> where T is	Members (continue)
	min_exponent	min_exponent10	max_exponent	max_exponent10	radix
float	FLT_MIN_EXP	FLT_MIN_10_EXP	FLT_MAX_EXP	FLT_MAX_10_EXP	FLT_RADIX
double	DBL_MIN_EXP	DBL_MIN_10_EXP	DBL_MAX_EXP	DBL_MAX_10_EXP	FLT_RADIX
long double	LDBL_MIN_EXP	LDBL_MIN_10_EXP	LDBL_MAX_EXP	LDBL_MAX_10_EXP	FLT_RADIX

Example

Run this code

#include <iostream>
#include <limits>
 
int main() 
{
    std::cout << "type\t│ lowest()\t│ min()\t\t│ max()\n"
              << "bool\t│ "
              << std::numeric_limits<bool>::lowest() << "\t\t│ "
              << std::numeric_limits<bool>::min() << "\t\t│ "
              << std::numeric_limits<bool>::max() << '\n'
              << "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'
              << "int\t│ "
              << std::numeric_limits<int>::lowest() << "\t│ "
              << std::numeric_limits<int>::min() << "\t│ "
              << std::numeric_limits<int>::max() << '\n'
              << "float\t│ "
              << std::numeric_limits<float>::lowest() << "\t│ "
              << std::numeric_limits<float>::min() << "\t│ "
              << std::numeric_limits<float>::max() << '\n'
              << "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()
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

Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
LWG 201	C++98	specializations for all fundamental types need to be provided	excluded non-arithmetic types
LWG 559	C++98	it was unclear whether the std::numeric_limits specialization for a cv-qualified type behaves as the same as the corresponding specialization for the cv-unqualified type	they have the same behavior

See also

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