c++解释器模式

1.解释器模式简介

   解释器模式（Interpreter Pattern）提供了评估语言的语法或表达式的方式，它属于行为型模式。这种模式实现了一个表达式接口，该接口解释一个特定的上下文。这种模式被用在 SQL 解析、符号处理引擎等。

2.源码实现

#include <iostream>
#include <string>

using namespace std;

class Context
{
public:
    Context(int num)
    {
        m_num = num;
    }

public:
    void setNum(int num)
    {
        m_num = num;
    }

    int getNum()
    {
        return m_num;
    }

    void setRes(int res)
    {
        m_res = res;
    }

    int getRes()
    {
        return m_res;
    }

private:
    int m_num;
    int m_res;
};

class Expression
{
public:
    virtual void interpreter(Context *context) = 0;
};

class PlusExpression : public Expression
{
public:
    virtual void interpreter(Context *context)
    {
        int num = context->getNum();
        num++;
        context->setNum(num);
        context->setRes(num);
    }
};

class MinusExpression : public Expression
{
public:
    virtual void interpreter(Context *context)
    {
        int num = context->getNum();
        num--;
        context->setNum(num);
        context->setRes(num);
    }
};

int main(int argc, char **argv)
{
    Context *pcxt = new Context(10);
    Expression *e1 = new PlusExpression();

    e1->interpreter(pcxt);
    cout << "PlusExpression: " << pcxt->getRes() << endl;

    Expression *e2 = new MinusExpression();

    e2->interpreter(pcxt);
    cout << "MinusExpression: " << pcxt->getRes() << endl;

    delete e1;
    delete e2;

    delete pcxt;

    return 0;
}

3.编译源码

$ g++ -o example example.cpp

4.运行及其结果

$ ./example
PlusExpression: 11
MinusExpression: 10