C++: common_type

개요

• 인자로 전달된 n개의 타입들이 변환할 수 있는 공통 타입으로 변환

예제

• 코드

    #include <iostream>
    #include <string>
    #include <type_traits>
    #include <typeinfo>

    using namespace std;

    class Base {};

    class Derived : public Base {};

    template <typename T1, typename T2>
    auto plus_t(T1 t1, T2 t2) -> typename common_type<T1, T2>::type {
    	return t1 + t2;
    }

    int main() {
    	cout << typeid(common_type<int, float, double>::type).name() << endl;
    	cout << typeid(common_type<char, int>::type).name() << endl;
    	cout << typeid(common_type<char *, string>::type).name() << endl;
    	cout << typeid(common_type<Base, Derived>::type).name() << endl;
    	cout << typeid(common_type<Base *, Derived *>::type).name() << endl;

    	cout << plus_t(1, 1) << endl;
    	cout << plus_t(1, 1.1) << endl;
    	cout << plus_t("a", string("a")) << endl;

    	return 0;
    }

• 실행 결과

    d
    i
    NSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE
    4Base
    P4Base
    2
    2.1
    aa