c++ 行为型模式-解释器(Interpreter)

 1 #include <iostream>
 2 #include <list>
 3 class Context 
 4 {  
 5 private:
 6     std::string m_input;
 7     std::string m_output;
 8 public:
 9     void SetInput(std::string str) { m_input = str; }
10     std::string GetInput() { return m_input; }
11     void SetOutput(std::string str) { m_output = str; }
12     std::string GetOutput() { return m_output; }
13 };
14 
15 class AbstractExpression {
16 public:
17     virtual void Interpret(Context* context) = 0;
18     virtual ~AbstractExpression() {}
19 };
20 
21 class TerminalExpression : public AbstractExpression 
22 {  // 终结符表达式
23 public:
24     void Interpret(Context* context) 
25     {
26         std::cout << "TerminalExpression: " << context->GetInput().c_str() << ", "
27             << context->GetOutput().c_str() << std::endl;
28     }
29 };
30 
31 class NonterminalExpression : public AbstractExpression 
32 {   // 非终结符表达式
33 private:
34     AbstractExpression* m_expression;
35 public:
36     NonterminalExpression(AbstractExpression* expression): m_expression(expression){}
37     void Interpret(Context* context) 
38     {
39         std::cout << "NonterminalExpression: " << context->GetInput().c_str() << ", " 
40             << context->GetOutput().c_str() << std::endl;
41         m_expression->Interpret(context);
42     }
43 };
44 
45 int main() {
46     Context* c = new Context();
47     c->SetInput("Hello");
48     c->SetOutput("World");
49 
50     AbstractExpression* exp1 = new TerminalExpression();
51     AbstractExpression* exp2 = new NonterminalExpression(exp1);
52     exp1->Interpret(c); 
53     exp2->Interpret(c); 
54     delete exp1;
55     delete exp2;
56     system("pause");
57 }