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hw03 #35

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Sduby22 wants to merge 1 commit into parallel101:main from Sduby22:hw03

Sduby22 commented Feb 11, 2022

总结

使用std::common_type<> 可以获得“共同类型”，原理是三元运算符的返回值类型为共同类型
在定义变长模板参数时，如果只有一个变长模板参数，则会默认实例化出来一个变长参数为空的实例出来，此时会报错因为std::variant必须至少提供一个模板参数
- 所以必须template <typename Arg, typename ... More>
发现std::variant 与 std::vector相加时无法匹配到定义的模板加法运算符函数
- 推测是此时模板参数无法推断，因为定义的模板函数第二个参数为std::variant<T1, T2>，此时加号右边是vector<double>。
- 如果手动定义指定模板类型，定义一个非模板函数的话，可以顺利通过编译，vector会被隐式转换为variant
- 此处不知道如何解决，所以只能把vector静态类型转换为variant


          hw03

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