给定一个语言，定义它的文法的一种表示，并定义一个解释器，这个解释器使用该表示来解释语言中的句子。

#include <iostream>
#include <string>
using namespace std;class Context { };class Expression {
public:virtual ~Expression() { }virtual void Interpret(const Context& c) = 0;
};class TerminalExpression :public Expression {
public:TerminalExpression(const string& statement) {_statement = statement;}void Interpret(const Context& c) {cout << this->_statement << " -- TerminalExpression" << endl;}private:string _statement;
};class NonterminalExpression :public Expression {
public:NonterminalExpression(Expression* expression, int times) {_expression = expression;_times = times;}void Interpret(const Context& c) {for (int i = 0; i < _times; i++) {_expression->Interpret(c);}}private:Expression *_expression;int _times;
};int main() {Context *c = new Context();Expression *tp = new TerminalExpression("echo");Expression *ntp = new NonterminalExpression(tp, 4);ntp->Interpret(*c);delete ntp;delete tp;delete c;return 0;
}