RL分析器
import java.util.ArrayList;
//lsh
import java.util.Scanner;
/**
*题目：LR1分析过程模拟
*说明：
* 首先要说句，这程序没有花大量的时间写，稍微写了下吧，能运行，兼容中间插入空格
* 无特殊功能，就只能判断一个语句是否符合给定文法和显示LR(1)分析过程
*要求:
* 本程序按照如下文法设计：
* E->E+T|T
* T->T*F|F
* F->(E)|i
*/
public class RL1Analysis {
String[][] sentence = new String[][]{//文法，也是内定了，当然要用到其他文法也可以，就只要这些参数改一下就可以了，但为了简单起见，字符不能使用带一撇的字符
{"E","E+T"},//E->E+T
{"E","T"},//E->T
{"T","T*F"},//T->T*F
{"T","F"},//T->F
{"F","(E)"},//F->(E)
{"F","i"}//F->i
};
String[][] table = new String[][]{//为了简单，LR分析表就手工输入了，那样输入也挺麻烦的，其实老师还忘了一个个东西给我们，给了我们分析表，就必须得给对应的文法才可以，还好，看出来那文法了
{"","i","+","*","(",")","#","E","T","F"},
{"S0","S5","","","S4","","","1","2","3"},
{"S1","","S6","","","","acc","","",""},
{"S2","","r2","S7","","r2","r2","","",""},
{"S3","","r4","r4","","r4","r4","","",""},
{"S4","S5","","","S4","","","8","2","3"},
{"S5","","r6","r6","","r6","r6","","",""},
{"S6","S5","","","S4 ","","r1","","9","3"},
{"S7","S5","","","S4","","","","","10"},
{"S8","","S6","","","S11","","","",""},
{"S9","","r1","S7","","r1","r1","","",""},
{"S10","","r3","r3","","r3","r3","","",""},
{"S11","","r5","r5","","r5","r5","","",""}
};
String in=null;
public RL1Analysis(){
this.printSentence();//打印文法
Scanner sc = new Scanner(System.in);
System.out.println("/n请输入一个句子：");
in = sc.nextLine().toString();
in = removeBlank(in);
int index=0;//记录输入串的索引位置
StringBuffer stateTrack = new StringBuffer("S0");//状态栈，初始时如S0
StringBuffer analysisTrack = new StringBuffer("#");//分析栈，初始放#
ArrayList
String operator = "";//记录分析表中对应的值
String staTrack="";
int x,y;//记录在分析表中的位置
boolean isOver=false;
System.out.println("/n语句分析过程如下：");
System.out.println("状态栈"+getBlank(26)+"符号栈"+getBlank(20)+"输入串/tACTION/tGOTO");
while(!isOver){
x=0;y=0;
String inS = in.charAt(index)+"";//输入串如今读到的位置
for(int i= 1;i
{
y = i;
break;
}
staTrack = stateTrack.substring(stateTrack.lastIndexOf("S"),stateTrack.length());//读取状态栈最上面一个状态
for(int i=1;i
x = i;
break;
}
operator = table[x][y];//分析表中对应位置的动作
if(operator.length()>0){
System.out.print(stateTrack+getBlank(16-stateTrack.length())+analysisTrack+getBlank(18-analysisTrack.length()-in.length()+index)+in.substring(index,in.length())+"/t"+operator);
if(operator.startsWith("S")){//移进
stateTrack.append(operator);
analysisTrack.append(inS);
index++;//输入串指针下移一位
}else if(operator.startsWith("r")){//规约
int m = Integer.parseInt(operator.substring(1,operator.length()))-1;//截取后面的数字，用于查产生式，还有一点，这是从1开始的
String liutemp = sentence[m][1];
list.add(sentence[m][1]+"=>"+sentence[m][0]);//规约步骤
if(analysisTrack.toString().endsWith(liutemp))
analysisTrack.delete(analysisTrack.length()-liutemp.length(),analysisTrack.length());//在分析栈除去产生式右部的字符串
else{
System.out.println("/n规约时出错！");
System.exit(0);
}
analysisTrack.append(sentence[m][0]);//加上产生式左部，就相当于规约了
int stindex=stateTrack.lastIndexOf("S");
for(int i=0;i
stateTrack.delete(stindex,stateTrack.length());//一次去掉去掉一个状态
stindex=stateTrack.lastIndexOf("S");
}
x = 0;y = 0;
staTrack = stateTrack.substring(stateTrack.lastIndexOf("S"),stateTrack.length());
for(int i=1;i
x = i;
break;
}
}
for(int i=1;i
y = i;
break;
}
}
operator = table[x][y];//得到GOTO值
System.out.print("/t"+operator);
if(operator.matches("//d+"))
stateTrack.append("S"+operator);
else{
System.out.println("/n待规约项出错！");
System.exit(0);
}
}else if(operator.equals("acc")){
System.out.println("/n该语句符合该合法！");
isOver=true;
}
System.out.println();
}else {
System.out.println("输入的语句不符合给定文法！");
System.exit(0);
}
}
System.out.println("该句子语法树自底向上生成过程：");
for(int i=0;i
}
public void printSentence(){
System.out.println("假定文法如下：");
for(int i=0;i
}
public String getBlank(int n){//打印n个连续空格
String blank="";
for(int i=0;i
return blank;
}
public String removeBlank(String s){//消除多余的空格，最后追加#
StringBuffer res = new StringBuffer(s);
int kong=res.indexOf(" ");
while(kong>=0){
res.delete(kong,kong+1);
kong=res.indexOf(" ");
}
if(s.indexOf("#")==-1)//如果没有#号
res.append("#");
return res.toString();
}
public static void main(String[] args){
new RL1Analysis();
}
}