Java/C++实现解释器模式---机器人控制程序

某机器人控制程序包含一些简单的英文指令，其文法规则如下：

expression ::= direction action distance | composite

composite ::= expression and expression

direction ::= ‘up’ | ‘down’ | ‘left’ | ‘right’

action ::= ‘move’ | ‘run’

distance ::= an integer //一个整数值

如输入：up move 5，则输出“向上移动5个单位”；输入：down run 10 and left move 20，则输出“向下移动10个单位再向左移动20个单位”。

类图：

Java代码：

import java.util.Stack;
public abstract class AbstractNode {
    public abstract String interpret();
}

public class ActionNode extends AbstractNode{
    private String action;  

    public ActionNode(String action) {
        this.action = action;
    }  

    //动作（移动方式）表达式的解释操作
    public String interpret() {
        if (action.equalsIgnoreCase("move")) {
            return "移动";
        }
        else if (action.equalsIgnoreCase("run")) {
            return "快速移动";
        }
        else {
            return "无效指令";
        }
    }
}

public class AndNode extends AbstractNode{
    private AbstractNode left; //And的左表达式
    private AbstractNode right; //And的右表达式  

    public AndNode(AbstractNode left, AbstractNode right) {
        this.left = left;
        this.right = right;
    }  

    //And表达式解释操作
    public String interpret() {
        return left.interpret() + "再" + right.interpret();
    }
}

public class DirectionNode extends AbstractNode{
    private String direction;  

    public DirectionNode(String direction) {
        this.direction = direction;
    }  

    //方向表达式的解释操作
    public String interpret() {
        if (direction.equalsIgnoreCase("up")) {
            return "向上";
        }
        else if (direction.equalsIgnoreCase("down")) {
            return "向下";
        }
        else if (direction.equalsIgnoreCase("left")) {
            return "向左";
        }
        else if (direction.equalsIgnoreCase("right")) {
            return "向右";
        }
        else {
            return "无效指令";
        }
    }
}

public class DistanceNode extends AbstractNode{
     private String distance;  

        public DistanceNode(String distance) {
            this.distance = distance;
        }  

    //距离表达式的解释操作
        public String interpret() {
            return this.distance;
        }
}

public class InstructionHandler {
     private String instruction;
        private AbstractNode node;
        public void handle(String instruction) {
            AbstractNode left = null, right = null;
            AbstractNode direction = null, action = null, distance = null;
            Stack stack = new Stack(); //声明一个栈对象用于存储抽象语法树
            String[] words = instruction.split(" "); //以空格分隔指令字符串
            for (int i = 0; i < words.length; i++) {
                //本实例采用栈的方式来处理指令，如果遇到“and”，则将其后的三个单词作为三个终结符表达式连成一个简单句子SentenceNode作为“and”的右表达式，而将从栈顶弹出的表达式作为“and”的左表达式，最后将新的“and”表达式压入栈中。
                if (words[i].equalsIgnoreCase("and")) {
                    left = (AbstractNode)stack.pop(); //弹出栈顶表达式作为左表达式
                    String word1= words[++i];
                    direction = new DirectionNode(word1);
                    String word2 = words[++i];
                    action = new ActionNode(word2);
                    String word3 = words[++i];
                    distance = new DistanceNode(word3);
                    right = new SentenceNode(direction,action,distance); //右表达式
                    stack.push(new AndNode(left,right)); //将新表达式压入栈中
                }
                //如果是从头开始进行解释，则将前三个单词组成一个简单句子SentenceNode并将该句子压入栈中
                else {
                    String word1 = words[i];
                    direction = new DirectionNode(word1);
                    String word2 = words[++i];
                    action = new ActionNode(word2);
                    String word3 = words[++i];
                    distance = new DistanceNode(word3);
                    left = new SentenceNode(direction,action,distance);
                    stack.push(left); //将新表达式压入栈中
                }
            }
            this.node = (AbstractNode)stack.pop(); //将全部表达式从栈中弹出
        }  

        public String output() {
            String result = node.interpret(); //解释表达式
            return result;
        }
}

public class SentenceNode extends AbstractNode{
    private AbstractNode direction;
    private AbstractNode action;
    private AbstractNode distance;  

    public SentenceNode(AbstractNode direction,AbstractNode action,AbstractNode distance) {
        this.direction = direction;
        this.action = action;
        this.distance = distance;
    }  

    //简单句子的解释操作
    public String interpret() {
        return direction.interpret() + action.interpret() + distance.interpret();
    }
}

public class Client {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
         String instruction1 = "up move 5 and down run 10 and left move 5";
         String instruction2="down run 10 and left move 20";
         InstructionHandler handler = new InstructionHandler();
         handler.handle(instruction1);
         String outString;
         outString = handler.output();
         System.out.println(outString);
         handler.handle(instruction2);
         outString = handler.output();
         System.out.println(outString);
    }

}

C++代码：

#include<iostream>
#include<stack>
#include <sstream>
#include<string>
using namespace std;
class AbstractNode {
public:
    virtual string interpret()=0;
};
class ActionNode:public AbstractNode{
private:
    string action;
public:
    ActionNode(string action) {
        this->action = action;
    }
    string interpret() {
        if (action=="move") {
            return "移动";
        }
        else if (action=="run") {
            return "快速移动";
        }
        else {
            return "无效指令";
        }
    }
};
class AndNode:public AbstractNode{
private:
    AbstractNode *left; //And的左表达式
    AbstractNode *right; //And的右表达式
public:
    AndNode(AbstractNode *left, AbstractNode *right) {
        this->left = left;
        this->right = right;
    }
    //And表达式解释操作
    string interpret() {
        return left->interpret() + "再" + right->interpret();
    }
};
class DirectionNode :public AbstractNode{
private:
    string direction;
public:
    DirectionNode(string direction) {
        this->direction = direction;
    }
    //方向表达式的解释操作
    string interpret() {
        if (direction=="up") {
            return "向上";
        }
        else if (direction=="down") {
            return "向下";
        }
        else if (direction=="left") {
            return "向左";
        }
        else if (direction=="right") {
            return "向右";
        }
        else {
            return "无效指令";
        }
    }
};
class DistanceNode:public AbstractNode{
private:
    string distance;
public:
    DistanceNode(string distance) {
        this->distance = distance;
    }
    //距离表达式的解释操作
    string interpret() {
        return this->distance;
    }
};
class SentenceNode:public AbstractNode{
private:
    AbstractNode *direction;
    AbstractNode *action;
    AbstractNode *distance;

public:
    SentenceNode(AbstractNode *direction,AbstractNode *action,AbstractNode *distance) {
        this->direction = direction;
        this->action = action;
        this->distance = distance;
    }
    //简单句子的解释操作
    string interpret() {
        return direction->interpret() + action->interpret() + distance->interpret();
    }
};
class InstructionHandler {
private:
    string instruction;
    AbstractNode *node;
public:
    void handle(string instruction) {
        AbstractNode *left = NULL, *right = NULL;
        AbstractNode *direction = NULL, *action = NULL, *distance = NULL;
        stack<AbstractNode*> stack; //声明一个栈对象用于存储抽象语法树
        istringstream str1(instruction);
        istringstream str2(instruction);
        string out;
        int j=0,k=0;
        int n;
        //以空格分隔指令字符串
        while (str1 >> out) {
            j++;
        }
        n=j;
        string words[n];
        string out2;
        while (str2 >> out2) {
            words[k]=out2;
            k++;
        }
        for (int i = 0; i <n; i++) {
        //本实例采用栈的方式来处理指令，如果遇到“and”，则将其后的三个单词作为三个终结符表达式连成一个简单句子SentenceNode作为“and”的右表达式，而将从栈顶弹出的表达式作为“and”的左表达式，最后将新的“and”表达式压入栈中。
            if (words[i]=="and") {
                left = stack.top(); //弹出栈顶表达式作为左表达式
                stack.pop();
                string word1= words[++i];
                direction = new DirectionNode(word1);
                string word2 = words[++i];
                action = new ActionNode(word2);
                string word3 = words[++i];
                distance = new DistanceNode(word3);
                right = new SentenceNode(direction,action,distance); //右表达式
                stack.push(new AndNode(left,right)); //将新表达式压入栈中
            }
            //如果是从头开始进行解释，则将前三个单词组成一个简单句子SentenceNode并将该句子压入栈中
            else {
                string word1 = words[i];
                direction = new DirectionNode(word1);
                string word2 = words[++i];
                action = new ActionNode(word2);
                string word3 = words[++i];
                distance = new DistanceNode(word3);
                left = new SentenceNode(direction,action,distance);
                stack.push(left); //将新表达式压入栈中
            }
        }
        this->node = stack.top(); //将全部表达式从栈中弹出
        stack.pop();
    }

    string output() {
        string result = node->interpret(); //解释表达式
        return result;
    }
};
int main(){
    string instruction1 = "up move 5 and down run 10 and left move 5";
    string instruction2="down run 10 and left move 20";
    InstructionHandler *handler = new InstructionHandler();
    handler->handle(instruction1);
    string outString;
    outString = handler->output();
    cout<<outString<<endl;
    handler->handle(instruction2);
    outString = handler->output();
    cout<<outString<<endl;
}

运行结果：