1 #include <iostream> 2 #include <list> 3 #include <string> 4 using namespace std; 5  6 class Context; 7  8 class AbstractExpression 9 {10 public:11     virtual void interpret(Context *) = 0;12 };13 14 class TerminalExpression : public AbstractExpression15 {16 public:17     void interpret(Context *context)18     {19         cout << "终端解释器" << endl;20     }21 };22 23 class NonterminalExpression : public AbstractExpression24 {25 public:26     void interpret(Context *context)27     {28         cout << "非终端解释器" << endl;29     }30 };31 32 class Context33 {34 public:35     string input, output;36 };37 38 int main()39 {40     Context *context = new Context(); 41     list<AbstractExpression*>  lt;42     lt.push_back(new TerminalExpression());43     lt.push_back(new NonterminalExpression());44     lt.push_back(new TerminalExpression());45     lt.push_back(new TerminalExpression());46     47     for (list<AbstractExpression*>::iterator iter = lt.begin(); iter != lt.end(); iter++)48     {49         (*iter)->interpret(context);50     }51     52     return 0;53 }54 // Result:55 /*56 终端解释器57 非终端解释器58 终端解释器59 终端解释器60 */