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    #include <vector>
    #include <string>
    #include <functional>
    #include <iostream>
 
    using namespace std;
 
    struct Object {
        template <typename T>
        Object(T t) : model(new Model<T>(t)) {
            cout << "construct object from T" << endl;
        }
        friend void print(string str) {
            cout << str << endl;
        }
        friend void print(int i) {
            cout << i << endl;
        }
        struct Concept {
            virtual void print() =0;
        };
        template <typename T>
        struct Model : Concept {
            Model(T t) : data(t) {}
            void print() {
                print(data);
            }
            T data;
        };
        Concept *model;
    };
 
    struct For {
        For() {
            cout << "default construct For" << endl;
        }
        For(Object o) {
            cout << "construct For from object and push back" << endl;
            objects.push_back(o);
        }
        For operator()(Object o) {
            cout << "push back object" << endl;
            objects.push_back(o);
            return *this;
        }
        void print() {
            for(auto o : objects) {
                o.model->print();
            }
        };
        vector<Object> objects;
    };
 
    int main() {
        auto heterogeneous = For(1)(string("hello"));
        function<void(int)> f = [](int i)->void{ cout << i << endl; };
        heterogeneous.print();
    }
 

prog.cpp: In instantiation of ‘void Object::Model<T>::print() [with T = std::__cxx11::basic_string<char>]’:
prog.cpp:58:5:   required from here
prog.cpp:26:22: error: no matching function for call to ‘Object::Model<std::__cxx11::basic_string<char> >::print(std::__cxx11::basic_string<char>&)’
                 print(data);
                 ~~~~~^~~~~~
prog.cpp:25:18: note: candidate: void Object::Model<T>::print() [with T = std::__cxx11::basic_string<char>]
             void print() {
                  ^~~~~
prog.cpp:25:18: note:   candidate expects 0 arguments, 1 provided
prog.cpp: In instantiation of ‘void Object::Model<T>::print() [with T = int]’:
prog.cpp:58:5:   required from here
prog.cpp:26:22: error: no matching function for call to ‘Object::Model<int>::print(int&)’
                 print(data);
                 ~~~~~^~~~~~
prog.cpp:25:18: note: candidate: void Object::Model<T>::print() [with T = int]
             void print() {
                  ^~~~~
prog.cpp:25:18: note:   candidate expects 0 arguments, 1 provided

Standard output is empty