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std:: ratio_less

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

若比率 R1 小于比率 R2 ，则提供值为 true 的成员常量 value 。否则， value 为 false 。

目录

辅助变量模板

template < class R1, class R2 >
constexpr bool ratio_less_v = ratio_less < 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 或可避免溢出的等效表达式成立则为 true ，否则为 false
(公开静态成员常量)

成员函数

operator bool
将对象转换为 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

运行此代码 
#include <iostream>
#include <ratio>
int main()
{
    using x = std::ratio<69, 90>;
    using y = std::ratio<70, 90>;
    if constexpr (std::ratio_less_v<x, y>)
        std::cout << x::num << '/' << x::den << " < "
                  << y::num << '/' << y::den << '\n';
}

输出： 

23/30 < 7/9

参见

(C++11)
在编译时比较两个 ratio 对象是否满足 大于 关系
(类模板)