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| // declval example #include <utility> // std::declval #include <iostream> // std::cout struct A { // abstract class virtual int value() = 0; }; class B : public A { // class with specific constructor int val_; public: B(int i,int j):val_(i*j){} int value() {return val_;} }; int main() { decltype(std::declval<A>().value()) a; // int a decltype(std::declval<B>().value()) b; // int b decltype(B(0,0).value()) c; // same as above (known constructor) a = b = B(10,2).value(); std::cout << a << '\n'; return 0; }
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