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Introduction
It is a Numeric limits type and it provides information about the properties of arithmetic types (either integral or floating-point) in the specific platform for which the library compiles.
Declaration
Following is the declaration for std::numeric_limits.
template <class T> numeric_limits;
C++11
template <class T> numeric_limits;
Parameters
T − It is a type of class.
Example
In below example for std::numeric_limits.
#include <limits>
#include <iostream>
int main() {
std::cout << "typetlowest typethighest typen";
std::cout << "intt"
<< std::numeric_limits<int>::lowest() << ''t''
<< std::numeric_limits<int>::max() << ''n'';
std::cout << "floatt"
<< std::numeric_limits<float>::lowest() << ''t''
<< std::numeric_limits<float>::max() << ''n'';
std::cout << "doublet"
<< std::numeric_limits<double>::lowest() << ''t''
<< std::numeric_limits<double>::max() << ''n'';
}
The sample output should be like this −
type lowest type highest type int -2147483648 2147483647 float -3.40282e+38 3.40282e+38 double -1.79769e+308 1.79769e+308
Template instantiations
The fundamental arithmetic types of C++98 should be like this −
| fundamental arithmetic types | |
|---|---|
| integral types | bool |
char |
|
wchar_t |
|
signed char |
|
short int |
|
int |
|
long int |
|
unsigned char |
|
unsigned short int |
|
unsigned int |
|
unsigned long int |
|
| floating point types | float |
double |
|
long double |
|
The fundamental arithmetic types of C++11 should be like this −
| fundamental arithmetic types | |
|---|---|
| integral types | bool |
char |
|
char16_t |
|
char32_t |
|
wchar_t |
|
signed char |
|
short int |
|
int |
|
long int |
|
long long int |
|
unsigned char |
|
unsigned short int |
|
unsigned int |
|
unsigned long int |
|
unsigned long long int |
|
| floating point types | float |
double |
|
long double |
|
Members
| member | type | property |
|---|---|---|
| is_specialized | bool |
It is true for all (i.e., those for which numeric_limits is specialized). and false for all other types. |
| min() | T |
It is a minimum finite value. For floating types with denormalization (variable number of exponent bits): minimum positive normalized value. Equivalent to CHAR_MIN, SCHAR_MIN, SHRT_MIN, INT_MIN, LONG_MIN, LLONG_MIN, FLT_MIN, BL_MIN, LDBL_MIN or |
| max() | T |
It is a maximum finite value. Equivalent to CHAR_MAX, SCHAR_MAX, UCHAR_MAX, SHRT_MAX, USHRT_MAX, INT_MAX, UINT_MAX, LONG_MAX, ULONG_MAX, LLONG_MAX, ULLONG_MAX, UINT_LEAST16_MAX, UINT_LEAST32_MAX, FLT_MAX, DBL_MAX or LDBL_MAX, depending on type. |
| lowest() | T |
It is a minimum finite value. (since C++11) For integral types: the same as min(). For floating-point types: implementation-dependent; generally, the negative of max(). |
| digits | int |
It is for integer types: number of non-sign bits (radix base digits) in the representation. For floating types: number of digits (in radix base) in the mantissa (equivalent to FLT_MANT_DIG, DBL_MANT_DIG or LDBL_MANT_DIG). |
| digits10 | int |
It is a number of digits (in decimal base), that can be represented without change. Equivalent to FLT_DIG, DBL_DIG or LDBL_DIG for floating types. |
| max_digits10 | int |
It is a number of digits (in decimal base), that required to ensure that values that differ are always differentiated. |
| is_signed | bool |
true if type is signed. |
| is_integer | bool |
true if type is integer. |
| is_exact | bool |
true if type uses exact representations. |
| radix | int |
It is for integer types: base of the representation. For floating types: base of the exponent of the representation (equivalent to FLT_RADIX). |
| epsilon() | T |
It is a machine epsilon (the difference between 1 and the least value greater than 1 that is representable). Equivalent to FLT_EPSILON, DBL_EPSILON or LDBL_EPSILON for floating types. |
| round_error() | T | It measures of the maximum rounding error. |
| min_exponent | int |
It is a minimum negative integer value such that radix raised to Equivalent to FLT_MIN_EXP, DBL_MIN_EXP or LDBL_MIN_EXP for floating types. |
| min_exponent10 | int |
It is a minimum negative integer value such that 10 raised to that power generates a normalized floating-point number. Equivalent to FLT_MIN_10_EXP, DBL_MIN_10_EXP or LDBL_MIN_10_EXP for floating types. |
| max_exponent | int |
It is a maximum integer value such that radix raised to Equivalent to FLT_MAX_EXP, DBL_MAX_EXP or LDBL_MAX_EXP for floating types. |
| max_exponent10 | int |
It is a maximum integer value such that 10 raised to that power generates a normalized finite floating-point number. Equivalent to FLT_MAX_10_EXP, DBL_MAX_10_EXP or LDBL_MAX_10_EXP for floating types. |
| has_infinity | bool |
true if the type has a representation for positive infinity. |
| has_quiet_NaN | bool |
true if the type has a representation for a quiet (non-signaling) “Not-a-Number”. |
| has_signaling_NaN | bool |
true if the type has a representation for a signaling “Not-a-Number”. |
| has_denorm | float_denorm_style |
It is a denormalized values (representations with a variable number of exponent bits). A type may have any of the following enum values − denorm_absent, if it does not allow denormalized values. denorm_present, if it allows denormalized values. denorm_indeterminate, if indeterminate at compile time. |
| has_denorm_loss | bool |
true if a loss of accuracy is detected as a denormalization loss, rather than an inexact result. |
| infinity() | T | It represents of positive infinity, if available. |
| quiet_NaN() | T | It represents of quiet (non-signaling) “Not-a-Number”, if available. |
| signaling_NaN() | T | It represents of signaling “Not-a-Number”, if available. |
| denorm_min() | T |
Minimum positive denormalized value. It is for types not allowing denormalized values: same as |
| is_iec559 | bool |
An IEC-559 type always has has_infinity, has_quiet_NaN and has_signaling_NaN set to |
| is_bounded | bool |
true if the set of values represented by the type is finite. |
| is_modulo | bool |
true if the type is modulo. A type is modulo if it is possible to add two positive numbers and have a result that wraps around to a third number that is less. |
| traps | bool |
true if trapping is implemented for the type. |
| tinyness_before | bool |
true if tinyness is detected before rounding. |
| round_style | float_round_style |
It is a rounding style. A type may have any of the following enum values − round_toward_zero, if it rounds toward zero. round_to_nearest, if it rounds to the nearest representable value. round_toward_infinity, if it rounds toward infinity. round_toward_neg_infinity, if it rounds toward negative infinity. round_indeterminate, if the rounding style is indeterminable at compile time. |
For all above types that are not fundamental arithmetic types, the default template definition is used −
C++98
template <class T> class numeric_limits {
public:
static const bool is_specialized = false;
static T min() throw();
static T max() throw();
static const int digits = 0;
static const int digits10 = 0;
static const bool is_signed = false;
static const bool is_integer = false;
static const bool is_exact = false;
static const int radix = 0;
static T epsilon() throw();
static T round_error() throw();
static const int min_exponent = 0;
static const int min_exponent10 = 0;
static const int max_exponent = 0;
static const int max_exponent10 = 0;
static const bool has_infinity = false;
static const bool has_quiet_NaN = false;
static const bool has_signaling_NaN = false;
static const float_denorm_style has_denorm = denorm_absent;
static const bool has_denorm_loss = false;
static T infinity() throw();
static T quiet_NaN() throw();
static T signaling_NaN() throw();
static T denorm_min() throw();
static const bool is_iec559 = false;
static const bool is_bounded = false;
static const bool is_modulo = false;
static const bool traps = false;
static const bool tinyness_before = false;
static const float_round_style round_style = round_toward_zero;
};
C++11
template <class T> class numeric_limits {
public:
static constexpr bool is_specialized = false;
static constexpr T min() noexcept { return T(); }
static constexpr T max() noexcept { return T(); }
static constexpr T lowest() noexcept { return T(); }
static constexpr int digits = 0;
static constexpr int digits10 = 0;
static constexpr bool is_signed = false;
static constexpr bool is_integer = false;
static constexpr bool is_exact = false;
static constexpr int radix = 0;
static constexpr T epsilon() noexcept { return T(); }
static constexpr T round_error() noexcept { return T(); }
static constexpr int min_exponent = 0;
static constexpr int min_exponent10 = 0;
static constexpr int max_exponent = 0;
static constexpr int max_exponent10 = 0;
static constexpr bool has_infinity = false;
static constexpr bool has_quiet_NaN = false;
static constexpr bool has_signaling_NaN = false;
static constexpr float_denorm_style has_denorm = denorm_absent;
static constexpr bool has_denorm_loss = false;
static constexpr T infinity() noexcept { return T(); }
static constexpr T quiet_NaN() noexcept { return T(); }
static constexpr T signaling_NaN() noexcept { return T(); }
static constexpr T denorm_min() noexcept { return T(); }
static constexpr bool is_iec559 = false;
static constexpr bool is_bounded = false;
static constexpr bool is_modulo = false;
static constexpr bool traps = false;
static constexpr bool tinyness_before = false;
};
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