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std::ratio_multiply

性病：：比率[医]倍增

Defined in header ​​
template< class R1, class R2 > using ratio_multiply = /* see below */;​​

别名模板std::ratio_multiply表示两个精确有理数相乘的结果。std::ratio专门性R1和R2...

结果是std::ratio专业化std::ratio<U, V>，以至于Num == R1::num * R2::num和Denom == R1::den * R2::den%28计算，没有算术溢出%29，U是std::ratio<Num, Denom>::num和V是std::ratio<Num, Denom>::den...

注记

如果U或V不能在std::intmax_t，这个节目的形式不太好。如果Num或Denom不能在std::intmax_t，除非实现产生正确的值，否则程序的格式是错误的。U和V...

上述定义要求std::ratio_multiply<R1, R2>已降至最低；例如，std::ratio_multiply<std::ratio<1, 6>,std::ratio<4, 5>>是与std::ratio<2, 15>...

例

二次

#include <iostream>
#include <ratio>
 
int main()
{
    typedef std::ratio<2, 3> two_third;
    typedef std::ratio<1, 6> one_sixth;
    typedef std::ratio_multiply<two_third, one_sixth> r;
    std::cout << "2/3 * 1/6 = " << r::num << '/' << r::den << '\n';
}

二次

产出：

二次

2/3 * 1/6 = 1/9

二次

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