1、理解解释器模式的动机，掌握该模式的结构；
2、能够利用解释器模式解决实际问题。
[实验任务一]：解释器模式
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”。
实验要求：
1. 提交类图；
2. 提交源代码；
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++) {
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++
#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") {
retu;
}
else if (direction=="right") {
return "向右";
}
else {
return "无效指令";
}
}
};
class DistanceNode:public AbstractNode{
private:
string distance;
public:
