std::ratio_equal

 

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编译时有理数算术
编译时整数序列
integer_sequence (C++14)

 

编译时有理数算术

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)

 

在标头 <ratio> 定义
template< class R1, class R2 > struct ratio_equal : std::integral_constant<bool, /* see below */> { };		(C++11 起)

若比例 R1 与 R2 相等，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_equal_v = ratio_equal<R1, R2>::value;		(C++17 起)

继承自 std::integral_constant

成员常量

value [静态]

如果 R1::num == R2::num && R1::den == R2::den 那么是 true，否则是 false (公开静态成员常量)

成员函数

operator bool	将对象转换到 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>

可能的实现

template< class R1, class R2 > struct ratio_equal : public std::integral_constant < bool, R1::num == R2::num && R1::den == R2::den > {};

示例

运行此代码

#include <iostream>
#include <ratio>
 
int main()
{
    if(std::ratio_equal<std::ratio<2,3>, std::ratio<4,6>>::value) {
        std::cout << "2/3 == 4/6\n";
    } else {
        std::cout << "2/3 != 4/6\n";
    }
}

输出：

2/3 == 4/6