#include <vector>
#include <iostream>
using namespace std;

class Context{
};

class AbstractExpression{
public:
	virtual Context& Interpret(Context& context)=0;
};

class TerminalExpression: public AbstractExpression{
public:
	Context& Interpret(Context& context){
    	cout<<"Called Terminal.Interpret()"<<endl;
    	return context;
  	}
};

class NonterminalExpression: public AbstractExpression{
	vector<AbstractExpression*>	subexpressions;
public:
	Context& Interpret(Context& context){
    	cout<<"Called Nonterminal.Interpret()"<<endl;
		for (auto &ex : subexpressions) context = ex->Interpret(context);
    	return context;
 	}
 	void AddSubexpression(AbstractExpression* ex){
 		subexpressions.push_back(ex);
	}
};

main(){
	Context context;
	TerminalExpression tex1;
	TerminalExpression tex2;
	NonterminalExpression ntex;
	ntex.AddSubexpression(&tex1);
	ntex.AddSubexpression(&tex2);
	TerminalExpression tex3;
	NonterminalExpression root;
	root.AddSubexpression(&tex3);
	root.AddSubexpression(&ntex);
    root.Interpret(context);
    return 0;
}