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std:: ratio_less_equal

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ratio_less_equal
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定义于头文件 <ratio>
template < class R1, class R2 >
struct ratio_less_equal : std:: integral_constant < bool , /* 见下文 */ > { } ;
(C++11 起)

如果比例 R1 小于或等于比例 R2 ，则提供成员常量 value 等于 true 。否则， value 为 false 。

目录

辅助变量模板

template < class R1, class R2 >
constexpr bool ratio_less_equal_v = ratio_less_equal < R1, R2 > :: value ;
(C++17 起)

继承自 std:: integral_constant

成员常量

value
[static]
若 R1 :: num * R2 :: den <= R2 :: num * R1 :: den 或等价的可避免溢出的表达式成立则为 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 类型，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

运行此代码 
#include <iostream>
#include <ratio>
int main()
{
    static_assert(std::ratio_less_equal<std::ratio<1, 2>, std::ratio<3, 4>>::value,
                  "1/2 <= 3/4");
    if (std::ratio_less_equal<std::ratio<10,11>, std::ratio<11,12>>::value)
        std::cout << "10/11 <= 11/12" "\n";
    static_assert(std::ratio_less_equal_v<std::ratio<10, 11>, std::ratio<11, 12>>);
    if constexpr (std::ratio_less_equal_v<std::ratio<10, 11>, std::ratio<11, 12>>)
        std::cout << "11/12 <= 12/13" "\n";
}

输出： 

10/11 <= 11/12
11/12 <= 12/13

参见

(C++11)
在编译期比较两个 ratio 对象是否相等
(类模板)
(C++11)
在编译期比较两个 ratio 对象是否不相等
(类模板)