设计模式(二十)解释器模式 C++

#include <iostream>
#include <string>
#include <list>
using namespace std;

//包含解释器之外的一些全局信息
class Context
{
public:
  Context() {}

  ~Context() {}
};


class AbstractExpression
{
public:
  virtual ~AbstractExpression() {}

  virtual void Interpret(const Context& c) {}

protected:
  AbstractExpression() {}
};

//终结符表达式
class TerminalExpression :public AbstractExpression
{
public:
  TerminalExpression(const string& statement)
  {
    this->_statement = statement;
  }

  ~TerminalExpression() {}

  void Interpret(const Context& c)
  {
    cout << this->_statement << " Terminal Expression..." << endl;
  }

private:
  string _statement;
};

//非终结符表达式  
class NonterminalExpression :public AbstractExpression
{
public:
  NonterminalExpression(const string& statement)
  {
    this->_statement = statement;
  }

  ~NonterminalExpression() {}

  void Interpret(const Context& c)
  {
    cout << this->_statement << " Nonterminal Expression..." << endl;
  }

private:
  string _statement;
};


//测试代码
int main(int argc, char* argv[])
{
  Context* c = new Context();

  list<AbstractExpression*> ls;

  ls.push_back(new TerminalExpression("A"));
  ls.push_back(new NonterminalExpression("B"));
  ls.push_back(new TerminalExpression("C"));
  ls.push_back(new NonterminalExpression("D"));

  list<AbstractExpression*>::iterator it = ls.begin();
  for (it; it != ls.end(); ++it)
  {
    (*it)->Interpret(*c);
  }

  cin.get();
  return 0;
}