解释器模式

解释器模式 为语言创建解释器

#include <iostream>
#include <string>

using namespace std;

struct Expression {
    virtual bool interpret(string context) = 0;
};

struct TerminalExpression : public Expression {
public:
    TerminalExpression(string data){
        this->data = data;
    }
    virtual bool interpret(string context) {
        string::size_type idx = context.find(data);
        if (idx != string::npos){
            return true;
        }
        return false;
    }

private:
    string data;
};

struct OrExpression : public Expression {
public:
    OrExpression(Expression *expr1, Expression *expr2) {
        this->expr1 = expr1;
        this->expr2 = expr2;
    }
    virtual bool interpret(string context) {
        return expr1->interpret(context) || expr2->interpret(context);
    }
private:
    Expression *expr1;
    Expression *expr2;
};

struct AndExpression : public Expression {
public:
    AndExpression(Expression *expr1, Expression *expr2) {
        this->expr1 = expr1;
        this->expr2 = expr2;
    }
    virtual bool interpret(string context) {
        return expr1->interpret(context) && expr2->interpret(context);
    }
private:
    Expression *expr1;
    Expression *expr2;
};

Expression *getMaleExpression(){
  Expression *robert = new TerminalExpression("Robert");
  Expression *john = new TerminalExpression("John");
  return new OrExpression(robert, john);
}

Expression *getMarriedWomanExpression() {
  Expression *julie = new TerminalExpression("Julie");
  Expression *married = new TerminalExpression("Married");
  return new AndExpression(julie, married);
}

int main(int argc, char **argv) {
    Expression *isMale = getMaleExpression();
    Expression *isMarriedWoman = getMarriedWomanExpression();

    cout << "John is male? " <<
        isMale->interpret("John") << endl;
    cout << "Julie is a married women? " <<
        isMarriedWoman->interpret("Married Julie") << endl;
}