C/C++编程：使用radio库进行分数的运算与比较

不念不忘少年蓝@ 2022-05-16 22:37 167阅读 0赞

算术

### std::ratio\_add ###

**作用：在编译时相加两个 `ratio` 对象**

#include <iostream>
    #include <ratio>
     
    int main()
    {
        using two_third = std::ratio<2, 3>;
        using one_sixth = std::ratio<1, 6>;
     
        using sum = std::ratio_add<two_third, one_sixth>;
        std::cout << "2/3 + 1/6 = " << sum::num << '/' << sum::den << '\n';
    }

![20210222151639256.png][]

### std::ratio\_subtract ###

**作用：在编译时相减两个 `ratio` 对象**

#include <iostream>
    #include <ratio>
     
    int main()
    {
        using two_third = std::ratio<2, 3>;
        using one_sixth = std::ratio<1, 6>;
     
        using diff = std::ratio_subtract<two_third, one_sixth>;
        std::cout << "2/3 - 1/6 = " << diff::num << '/' << diff::den << '\n';
    }

![20210222151749505.png][]

### std::ratio\_multiply ###

作用：在编译时相乘两个 `ratio` 对象

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

![20210222152031148.png][]

### std::ratio\_divide ###

作用：在编译时相除两个 `ratio` 对象

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

![20210222152108795.png][]

## 比较 ##

## std::ratio\_equal ##

作用：在编译时比较两个 `ratio` 对象的相等性

#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";
        }
    }

![20210222152222681.png][]

### std::ratio\_not\_equal ###

作用：在编译时比较两个 `ratio` 对象的不相等性

#include <iostream>
    #include <ratio>
     
    int main()
    {
        if(std::ratio_not_equal<std::ratio<2,3>, std::ratio<1,3>>::value) {
            std::cout << "2/3 != 1/3\n";
        } else {
            std::cout << "2/3 == 1/3\n";
        }
    }

![20210222152309437.png][]

### std::ratio\_less ###

作用： 在编译时比较两个 `ratio` 对象的*小于*关系

#include <iostream>
    #include <ratio>
     
    int main()
    {
        if (std::ratio_less<std::ratio<23,37>, std::ratio<57,90>>::value) {
            std::cout << "23/37 < 57/90\n";
        }
    }

### ![20210222152822948.png][] ###

### std::ratio\_less\_equal ###

作用：在编译时比较两个 `ratio` 对象的*小于或等于*关系

#include <ratio>
    #include <iostream>
     
    auto main() -> int
    {
        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";
        }
     
        // C++17 起
        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";
        }
    }

![20210222152738216.png][]

### std::ratio\_greater ###

作用：在编译时比较两个 `ratio` 对象的*大于*关系

#include <ratio>
    #include <iostream>
     
    auto main() -> int
    {
        static_assert(std::ratio_greater<std::ratio<3, 4>, std::ratio<1, 2>>::value,
                      "3/4 > 1/2");
     
        if (std::ratio_greater<std::ratio<11, 12>, std::ratio<10, 11>>::value) {
            std::cout << "11/12 > 10/11" "\n";
        }
     
        // Since C++17
        static_assert(std::ratio_greater_v<std::ratio<12, 13>, std::ratio<11, 12>> );
     
        if constexpr (std::ratio_greater_v<std::ratio<12, 13>, std::ratio<11, 12>>) {
            std::cout << "12/13 > 11/12" "\n";
        }
    }

### ![20210222152706648.png][] ###

### std::ratio\_greater\_equal ###

作用：在编译时比较两个 `ratio` 对象的*大于或等于*关系

#include <ratio>
    #include <iostream>
     
    auto main() -> int
    {
        static_assert(std::ratio_greater_equal<
            std::ratio<2, 3>, 
            std::ratio<2, 3>>::value, "2/3 >= 2/3");
     
        if (std::ratio_greater_equal<
            std::ratio<2,1>, std::ratio<1, 2>>::value) {
            std::cout << "2/1 >= 1/2" "\n";
        }
     
        if (std::ratio_greater_equal<
            std::ratio<1,2>, std::ratio<1, 2>>::value) {
            std::cout << "1/2 >= 1/2" "\n";
        }
     
        // C++17 起
        static_assert(std::ratio_greater_equal_v<
            std::ratio<999'999, 1'000'000>, 
            std::ratio<999'998, 999'999>> );
     
        if constexpr (std::ratio_greater_equal_v<
            std::ratio<999'999, 1'000'000>, 
            std::ratio<999'998, 999'999>>) {
            std::cout << "999'999/1'000'000 >= 999'998/999'999" "\n";
        }
        if constexpr (std::ratio_greater_equal_v<
            std::ratio<999'999, 1'000'000>, 
            std::ratio<999'999, 1'000'000>>) {
            std::cout << "999'999/1'000'000 >= 999'999/1'000'000" "\n";
        }
    }

![20210222152603845.png][]

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[20210222152309437.png]: /images/20220517/19ecfa44653a4ec485219242c3546d99.png
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