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std::ratio_greater_equal

来自cppreference.com
< cpp‎ | numeric‎ | ratio
定义于头文件 <ratio>
template< class R1, class R2 >
struct ratio_greater_equal : std::integral_constant<bool, /* see below */> { };
(C++11 起)

若比例 R1 大于或等于比例 R2 ,则提供等于 true 的成员常量 value 。否则 value 等于 false

辅助变量模板

template< class R1, class R2 >
inline constexpr bool ratio_greater_equal_v = ratio_greater_equal<R1, R2>::value;
(C++17 起)

继承自 std::integral_constant

成员常量

value
[静态]
R1::num * R2::den >= R2::num * R1::den 或避免溢出的等价表达式成立,则为 true ,否则为 false
(公开静态成员常量)

成员函数

operator bool
转换对象为 bool ,返回 value
(公开成员函数)
operator()
(C++14)
返回 value
(公开成员函数)

成员类型

 
类型 定义
value_type bool
type std::integral_constant<bool, value>

示例

#include <ratio>
#include <iostream>
 
auto main() -> int
{
    static_assert(std::ratio_greater_equal<
        std::ratio<2, 3>, 
        std::ratio<2, 3>>::value, "2/3 >= 2/3");
 
    if (std::ratio_greater_equal<
        std::ratio<2,1>, std::ratio<1, 2>>::value) {
        std::cout << "2/1 >= 1/2" "\n";
    }
 
    if (std::ratio_greater_equal<
        std::ratio<1,2>, std::ratio<1, 2>>::value) {
        std::cout << "1/2 >= 1/2" "\n";
    }
 
    // C++17 起
    static_assert(std::ratio_greater_equal_v<
        std::ratio<999'999, 1'000'000>, 
        std::ratio<999'998, 999'999>> );
 
    if constexpr (std::ratio_greater_equal_v<
        std::ratio<999'999, 1'000'000>, 
        std::ratio<999'998, 999'999>>) {
        std::cout << "999'999/1'000'000 >= 999'998/999'999" "\n";
    }
    if constexpr (std::ratio_greater_equal_v<
        std::ratio<999'999, 1'000'000>, 
        std::ratio<999'999, 1'000'000>>) {
        std::cout << "999'999/1'000'000 >= 999'999/1'000'000" "\n";
    }
}

输出:

2/1 >= 1/2
1/2 >= 1/2
999'999/1'000'000 >= 999'998/999'999
999'999/1'000'000 >= 999'999/1'000'000

参阅

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