std::ratio_less

 

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编译时有理数运算
编译时整数序列
integer_sequence (C++14)

 

编译时有理数运算

ratio (C++11)

算术

ratio_add (C++11)

ratio_subtract (C++11)

ratio_multiply (C++11)

ratio_divide (C++11)

比较

ratio_equal (C++11)

ratio_not_equal (C++11)

ratio_less (C++11)

ratio_less_equal (C++11)

ratio_greater (C++11)

ratio_greater_equal (C++11)

 

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

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

辅助变量模板

template< class R1, class R2 > constexpr bool ratio_less_v = ratio_less<R1, R2>::value;		(自 C++17 起)

继承自 std::integral_constant

成员常量

value [静态]

true 如果 R1::num * R2::den < R2::num * R1::den，或等效表达式可以避免溢出，否则为 false (公有静态成员常量)

成员函数

operator bool	将对象转换为 bool，返回 value (公有成员函数)
operator() (C++14)	返回 value (公有成员函数)

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

另请参见

ratio_greater (C++11)

在编译时比较两个 ratio 对象以判断是否大于 (类模板)