std::numeric_limits<T>::max
来自 cppreference.cn
< cpp | 类型 | numeric_limits
| 定义于头文件 <limits> |
||
static T max() throw(); |
(直到 C++11) | |
| static constexpr T max() noexcept; |
(自 C++11 起) | |
返回数值类型 T 所能表示的最大有限值。对所有有界类型有意义。
[编辑] 返回值
T
|
std::numeric_limits<T>::max() |
| /* 非特化 */ | T() |
| bool | true |
| char | CHAR_MAX |
| signed char | SCHAR_MAX |
| unsigned char | UCHAR_MAX |
| wchar_t | WCHAR_MAX |
| char8_t (自 C++20 起) | UCHAR_MAX |
| char16_t (自 C++11 起) | UINT_LEAST16_MAX |
| char32_t (自 C++11 起) | UINT_LEAST32_MAX |
| short | SHRT_MAX |
| unsigned short | USHRT_MAX |
| int | INT_MAX |
| unsigned int | UINT_MAX |
| long | LONG_MAX |
| unsigned long | ULONG_MAX |
| long long (自 C++11 起) | LLONG_MAX |
| unsigned long long (自 C++11 起) | ULLONG_MAX |
| float | FLT_MAX |
| double | DBL_MAX |
| long double | LDBL_MAX |
[编辑] 示例
演示 max() 与一些基本类型和一些标准库 typedef 的用法（输出是系统特定的）
运行此代码
#include <boost/type_index.hpp> #include <cstddef> #include <iomanip> #include <iostream> #include <limits> #include <type_traits> template<typename T> void print_max_value_of() { constexpr T max{std::numeric_limits<T>::max()}; std::cout << std::setw(16) << boost::typeindex::type_id<T>() << ": "; if constexpr (std::is_floating_point_v<T>) std::cout << std::defaultfloat << max << " = " << std::hexfloat << max << '\n'; else { constexpr auto m{static_cast<unsigned long long>(max)}; std::cout << std::dec << m << " = " << std::hex << m << '\n'; } } int main() { std::cout << std::showbase; print_max_value_of<bool>(); print_max_value_of<short>(); print_max_value_of<int>(); print_max_value_of<std::streamsize>(); print_max_value_of<std::size_t>(); print_max_value_of<char>(); print_max_value_of<char16_t>(); print_max_value_of<wchar_t>(); print_max_value_of<float>(); print_max_value_of<double>(); print_max_value_of<long double>(); }
可能的输出
bool: 1 = 0x1
short: 32767 = 0x7fff
int: 2147483647 = 0x7fffffff
long: 9223372036854775807 = 0x7fffffffffffffff
unsigned long: 18446744073709551615 = 0xffffffffffffffff
char: 127 = 0x7f
char16_t: 65535 = 0xffff
wchar_t: 2147483647 = 0x7fffffff
float: 3.40282e+38 = 0x1.fffffep+127
double: 1.79769e+308 = 0x1.fffffffffffffp+1023
long double: 1.18973e+4932 = 0xf.fffffffffffffffp+16380[编辑] 参见
| [静态] (C++11) |
返回给定类型的最小有限值，即有符号类型的最负值，无符号类型的 0 (public static member function) |
| [静态] |
返回给定非浮点类型的最小有限值，或给定浮点类型的最小正规值 (public static member function) |
