解释器模式

 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 AbstractExpression
15 {
16 public:
17     void interpret(Context *context)
18     {
19         cout << "终端解释器" << endl;
20     }
21 };
22 
23 class NonterminalExpression : public AbstractExpression
24 {
25 public:
26     void interpret(Context *context)
27     {
28         cout << "非终端解释器" << endl;
29     }
30 };
31 
32 class Context
33 {
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 */