std::numeric_limits<T>::min
來自 cppreference.com
| 定義於標頭檔案 <limits> |
||
static T min() throw(); |
(C++11 前) | |
| static constexpr T min() noexcept; |
(C++11 起) | |
返回數字型別 T 可表示的最小有限值。
對於支援非規格化（denormalization）的浮點型別，min() 返回最小的正規格化值。請注意，此行為可能出乎意料，尤其與整數型別的 min() 行為相比。 要查詢沒有比它更小的值的值，請使用 lowest()。(C++11 起)
min() 僅對有界型別和無符號無界型別有意義。
[編輯] 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 |
[編輯] 示例
演示了與 typedef 型別的使用，以及整數和浮點型別結果符號的差異
執行此程式碼
#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); }
可能的輸出
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[編輯] 參閱
| [靜態] (C++11) |
返回給定型別的最低有限值，即有符號型別的最負值，無符號型別的 0 (public static member function) |
| [靜態] |
返回給定浮點型別的最小正非正規化值 (public static member function) |
| [靜態] |
返回給定型別的最大有限值 (public static member function) |
