std::numeric_limits<T>::min
来自 cppreference.cn
| 定义于头文件 <limits> |
||
static T min() throw(); |
(C++11 前) | |
| static constexpr T min() noexcept; |
(C++11 起) | |
返回数字类型 T 可表示的最小有限值。
对于支持非规格化（denormalization）的浮点类型，min() 返回最小的正规格化值。请注意，此行为可能出乎意料，尤其与整数类型的 min() 行为相比。 要查找没有比它更小的值的值，请使用 lowest()。(C++11 起)
min() 仅对有界类型和无符号无界类型有意义。
[编辑] 返回值
T
|
std::numeric_limits<T>::min() |
| /* 未特化 */ | T() |
| bool | false |
| char | CHAR_MIN |
| signed char | SCHAR_MIN |
| unsigned char | 0 |
| wchar_t | WCHAR_MIN |
| char8_t (C++20起) | 0 |
| char16_t (C++11起) | 0 |
| char32_t (C++11起) | 0 |
| short | SHRT_MIN |
| unsigned short | 0 |
| int | INT_MIN |
| unsigned int | 0 |
| long | LONG_MIN |
| unsigned long | 0 |
| long long (C++11起) | LLONG_MIN |
| unsigned long long (C++11起) | 0 |
| float | FLT_MIN |
| double | DBL_MIN |
| long double | LDBL_MIN |
[编辑] 示例
演示了与 typedef 类型的使用，以及整数和浮点类型结果符号的差异
运行此代码
#include <cstddef> #include <iomanip> #include <iostream> #include <limits> // we want to print char types as an integer without leading Fs auto p(auto x) { return x; } auto p(char x) { return x & static_cast<unsigned char>(-1); } template <typename T> void print_one(std::string_view type_name) { constexpr T min = std::numeric_limits<T>::min(); std::cout << std::dec << std::defaultfloat << std::setw(14) << type_name << " (" << std::setw(2) << sizeof(T) << " bytes): " << +min; if constexpr (min != 0) std::cout << " or " << std::showbase << std::hex << std::hexfloat << p(min); std::cout << '\n'; } #define SHOW(T) print_one<T>(#T) int main() { SHOW(bool); SHOW(char); SHOW(unsigned char); SHOW(short); SHOW(unsigned short); SHOW(signed); SHOW(unsigned); SHOW(std::ptrdiff_t); SHOW(std::size_t); SHOW(float); SHOW(double); SHOW(long double); }
可能的输出
bool ( 1 bytes): 0
char ( 1 bytes): -128 or 0x80
unsigned char ( 1 bytes): 0
short ( 2 bytes): -32768 or 0x8000
unsigned short ( 2 bytes): 0
signed ( 4 bytes): -2147483648 or 0x80000000
unsigned ( 4 bytes): 0
std::ptrdiff_t ( 8 bytes): -9223372036854775808 or 0x8000000000000000
std::size_t ( 8 bytes): 0
float ( 4 bytes): 1.17549e-38 or 0x1p-126
double ( 8 bytes): 2.22507e-308 or 0x1p-1022
long double (16 bytes): 3.3621e-4932 or 0x8p-16385[编辑] 参阅
| [静态] (C++11) |
返回给定类型的最低有限值，即有符号类型的最负值，无符号类型的 0 (public static member function) |
| [静态] |
返回给定浮点类型的最小正非正规化值 (public static member function) |
| [静态] |
返回给定类型的最大有限值 (public static member function) |
