C++ 中支持 std::numeric_limits() 的数据类型
numeric_limits 类模板提供了一种简单且标准化的方法来查询算术类型的各种属性。例如，类型 T 可以存储的最大值是std::numeric_limits
例子：
- std::numeric_limits
::max() 给出了我们可以存储在 int 类型中的最大可能值。 - std::numeric_limits
::max()) 给出了我们可以存储在 unsigned int 类型中的最大可能值。
numeric_limits有许多成员函数、成员常量和辅助类，其中一些是特定于类型的。例如std::numeric_limits
- std::numeric_limits
::is_integer： 若 T 为数值类型则为真，浮点类型为假。 - std::numeric_limits
::is_signed： 对于所有有符号算术类型 T 为真，对于无符号类型为假。 - std::numeric_limits
::digits： 它是基数的位数。例如--1 代表 bool，7 代表 char，31 代表 int，等等。 - std::numeric_limits
::digits10： 它是可以由类型 T 表示而无需任何更改的以 10 为底的数字的数量。 - std::numeric_limits
::max_digits10： 它是唯一表示类型 T 的所有不同值所需的基数为 10 的数字的数量。 - 此外，查询最小值、最大值、最小值、字节大小和位。
浮点数具有与 epsilon 相关的查询。除了这些， numeric_limits还有一些功能。例如： has_infinity 、 traps 、 round_error等。
下面是显示所有数据类型最常见的numeric_limits函数的程序：
C++
// C++ program to demonstrate the use
// possible numerical data types
// that supports std::numeric_limits
#include
#include
#include
#include
#include
#include
struct RowPrinter {
// Left alignment
int m_left;
// Right alignment
int m_right;
RowPrinter(int left, int right)
: m_left(left), m_right(right)
{
// Print bool as 'true' or 'false'
// instead of 0 or 1.
std::cout << std::boolalpha;
}
template
auto printRow(const std::string& label,
const A& value) const -> void
{
std::cout << std::setw(m_left) << label
<< std::setw(m_right) << value << "\n";
}
};
#define SHOW_INTEGER_LIMITS(numtype) \
showNumericLimits(#numtype)
#define SHOW_FLOAT_LIMITS(numtype) \
showFloatPointLimits(#numtype)
// Function to show the numeric
// limits
template
void showNumericLimits(const std::string& name)
{
RowPrinter rp{ 30, 25 };
std::cout << "Numeric limits for type: " << name
<< "\n";
std::cout << std::string(60, '-') << "\n";
rp.printRow("Type:", name);
rp.printRow("Is integer:",
std::numeric_limits::is_integer);
rp.printRow("Is signed:",
std::numeric_limits::is_signed);
rp.printRow("Number of digits:",
std::numeric_limits::digits);
rp.printRow("Number of digits 10:",
std::numeric_limits::digits10);
rp.printRow("Max Number of digits 10:",
std::numeric_limits::max_digits10);
// RTTI - Run-Time Type Information
if (typeid(T) == typeid(uint8_t)
|| typeid(T) == typeid(int8_t)
|| typeid(T) == typeid(bool)
|| typeid(T) == typeid(char)
|| typeid(T) == typeid(unsigned char)) {
// Min Abs - smallest positive value
// for float point numbers
rp.printRow("Min:",
static_cast(
std::numeric_limits::min()));
// Smallest value (can be negative)
rp.printRow("Lowest:",
static_cast(
std::numeric_limits::lowest()));
// Largest value
rp.printRow("Max:",
static_cast(
std::numeric_limits::max()));
}
else {
rp.printRow("Min:", std::numeric_limits::min());
rp.printRow("Lowest:",
std::numeric_limits::lowest());
rp.printRow("Max:", std::numeric_limits::max());
}
rp.printRow("Size in bytes:", sizeof(T));
rp.printRow("Size in bits:", 8 * sizeof(T));
std::cout << "\n";
}
// Function to show float points
// limits
template
void showFloatPointLimits(const std::string& name)
{
RowPrinter rp{ 30, 25 };
showNumericLimits(name);
rp.printRow("Epsilon:",
std::numeric_limits::epsilon());
rp.printRow("Min exponent:",
std::numeric_limits::min_exponent10);
rp.printRow("Max exponent:",
std::numeric_limits::max_exponent10);
}
// Driver Code
int main()
{
// Boolean type
SHOW_INTEGER_LIMITS(bool);
// Character types
SHOW_INTEGER_LIMITS(char);
SHOW_INTEGER_LIMITS(unsigned char);
SHOW_INTEGER_LIMITS(wchar_t);
// Standard integers in
SHOW_INTEGER_LIMITS(int8_t);
SHOW_INTEGER_LIMITS(uint8_t);
SHOW_INTEGER_LIMITS(int16_t);
SHOW_INTEGER_LIMITS(uint16_t);
SHOW_INTEGER_LIMITS(int32_t);
SHOW_INTEGER_LIMITS(uint32_t);
SHOW_INTEGER_LIMITS(int64_t);
SHOW_INTEGER_LIMITS(uint64_t);
// Integer types
SHOW_INTEGER_LIMITS(short);
SHOW_INTEGER_LIMITS(unsigned short);
SHOW_INTEGER_LIMITS(int);
SHOW_INTEGER_LIMITS(unsigned int);
SHOW_INTEGER_LIMITS(long);
SHOW_INTEGER_LIMITS(unsigned long);
SHOW_INTEGER_LIMITS(long long);
SHOW_INTEGER_LIMITS(unsigned long long);
// Floating types
SHOW_FLOAT_LIMITS(float);
SHOW_FLOAT_LIMITS(double);
SHOW_FLOAT_LIMITS(long double);
return 0;
} 输出：
Numeric limits for type: bool
------------------------------------------------------------
Type: bool
Is integer: true
Is signed: false
Number of digits: 1
Number of digits 10: 0
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 1
Size in bytes: 1
Size in bits: 8
Numeric limits for type: char
------------------------------------------------------------
Type: char
Is integer: true
Is signed: true
Number of digits: 7
Number of digits 10: 2
Max Number of digits 10: 0
Min: -128
Lowest: -128
Max: 127
Size in bytes: 1
Size in bits: 8
Numeric limits for type: unsigned char
------------------------------------------------------------
Type: unsigned char
Is integer: true
Is signed: false
Number of digits: 8
Number of digits 10: 2
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 255
Size in bytes: 1
Size in bits: 8
Numeric limits for type: wchar_t
------------------------------------------------------------
Type: wchar_t
Is integer: true
Is signed: true
Number of digits: 31
Number of digits 10: 9
Max Number of digits 10: 0
Min: -2147483648
Lowest: -2147483648
Max: 2147483647
Size in bytes: 4
Size in bits: 32
Numeric limits for type: int8_t
------------------------------------------------------------
Type: int8_t
Is integer: true
Is signed: true
Number of digits: 7
Number of digits 10: 2
Max Number of digits 10: 0
Min: -128
Lowest: -128
Max: 127
Size in bytes: 1
Size in bits: 8
Numeric limits for type: uint8_t
------------------------------------------------------------
Type: uint8_t
Is integer: true
Is signed: false
Number of digits: 8
Number of digits 10: 2
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 255
Size in bytes: 1
Size in bits: 8
Numeric limits for type: int16_t
------------------------------------------------------------
Type: int16_t
Is integer: true
Is signed: true
Number of digits: 15
Number of digits 10: 4
Max Number of digits 10: 0
Min: -32768
Lowest: -32768
Max: 32767
Size in bytes: 2
Size in bits: 16
Numeric limits for type: uint16_t
------------------------------------------------------------
Type: uint16_t
Is integer: true
Is signed: false
Number of digits: 16
Number of digits 10: 4
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 65535
Size in bytes: 2
Size in bits: 16
Numeric limits for type: int32_t
------------------------------------------------------------
Type: int32_t
Is integer: true
Is signed: true
Number of digits: 31
Number of digits 10: 9
Max Number of digits 10: 0
Min: -2147483648
Lowest: -2147483648
Max: 2147483647
Size in bytes: 4
Size in bits: 32
Numeric limits for type: uint32_t
------------------------------------------------------------
Type: uint32_t
Is integer: true
Is signed: false
Number of digits: 32
Number of digits 10: 9
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 4294967295
Size in bytes: 4
Size in bits: 32
Numeric limits for type: int64_t
------------------------------------------------------------
Type: int64_t
Is integer: true
Is signed: true
Number of digits: 63
Number of digits 10: 18
Max Number of digits 10: 0
Min: -9223372036854775808
Lowest: -9223372036854775808
Max: 9223372036854775807
Size in bytes: 8
Size in bits: 64
Numeric limits for type: uint64_t
------------------------------------------------------------
Type: uint64_t
Is integer: true
Is signed: false
Number of digits: 64
Number of digits 10: 19
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 18446744073709551615
Size in bytes: 8
Size in bits: 64
Numeric limits for type: short
------------------------------------------------------------
Type: short
Is integer: true
Is signed: true
Number of digits: 15
Number of digits 10: 4
Max Number of digits 10: 0
Min: -32768
Lowest: -32768
Max: 32767
Size in bytes: 2
Size in bits: 16
Numeric limits for type: unsigned short
------------------------------------------------------------
Type: unsigned short
Is integer: true
Is signed: false
Number of digits: 16
Number of digits 10: 4
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 65535
Size in bytes: 2
Size in bits: 16
Numeric limits for type: int
------------------------------------------------------------
Type: int
Is integer: true
Is signed: true
Number of digits: 31
Number of digits 10: 9
Max Number of digits 10: 0
Min: -2147483648
Lowest: -2147483648
Max: 2147483647
Size in bytes: 4
Size in bits: 32
Numeric limits for type: unsigned int
------------------------------------------------------------
Type: unsigned int
Is integer: true
Is signed: false
Number of digits: 32
Number of digits 10: 9
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 4294967295
Size in bytes: 4
Size in bits: 32
Numeric limits for type: long
------------------------------------------------------------
Type: long
Is integer: true
Is signed: true
Number of digits: 63
Number of digits 10: 18
Max Number of digits 10: 0
Min: -9223372036854775808
Lowest: -9223372036854775808
Max: 9223372036854775807
Size in bytes: 8
Size in bits: 64
Numeric limits for type: unsigned long
------------------------------------------------------------
Type: unsigned long
Is integer: true
Is signed: false
Number of digits: 64
Number of digits 10: 19
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 18446744073709551615
Size in bytes: 8
Size in bits: 64
Numeric limits for type: long long
------------------------------------------------------------
Type: long long
Is integer: true
Is signed: true
Number of digits: 63
Number of digits 10: 18
Max Number of digits 10: 0
Min: -9223372036854775808
Lowest: -9223372036854775808
Max: 9223372036854775807
Size in bytes: 8
Size in bits: 64
Numeric limits for type: unsigned long long
------------------------------------------------------------
Type: unsigned long long
Is integer: true
Is signed: false
Number of digits: 64
Number of digits 10: 19
Max Number of digits 10: 0
Min: 0
Lowest: 0
Max: 18446744073709551615
Size in bytes: 8
Size in bits: 64
Numeric limits for type: float
------------------------------------------------------------
Type: float
Is integer: false
Is signed: true
Number of digits: 24
Number of digits 10: 6
Max Number of digits 10: 9
Min: 1.17549e-38
Lowest: -3.40282e+38
Max: 3.40282e+38
Size in bytes: 4
Size in bits: 32
Epsilon: 1.19209e-07
Min exponent: -37
Max exponent: 38
Numeric limits for type: double
------------------------------------------------------------
Type: double
Is integer: false
Is signed: true
Number of digits: 53
Number of digits 10: 15
Max Number of digits 10: 17
Min: 2.22507e-308
Lowest: -1.79769e+308
Max: 1.79769e+308
Size in bytes: 8
Size in bits: 64
Epsilon: 2.22045e-16
Min exponent: -307
Max exponent: 308
Numeric limits for type: long double
------------------------------------------------------------
Type: long double
Is integer: false
Is signed: true
Number of digits: 64
Number of digits 10: 18
Max Number of digits 10: 21
Min: 3.3621e-4932
Lowest: -1.18973e+4932
Max: 1.18973e+4932
Size in bytes: 16
Size in bits: 128
Epsilon: 1.0842e-19
Min exponent: -4931
Max exponent: 4932想要从精选的视频和练习题中学习，请查看C++ 基础课程，从基础到高级 C++ 和C++ STL 课程，了解基础加 STL。要完成从学习语言到 DS Algo 等的准备工作，请参阅完整的面试准备课程。