编译语言-语法分析器的设计

实验三语法分析器的设计

一、实验内容

设计、编写和调试构造LR（0）项目集规范簇或实现基于LR分析表对给定的符号串进行LR 分析的程序。以下两个内容任选其中一项：

（1）对于给定的文法，实现构造识别该文法全部活前缀DFA的程序。

（2）对于给定的LR分析表和符号串，设计程序以实现所输入符号串是否为合法符号串。

要求用JAVA语言编程。（可参考实验指导书P149至P156）

二、程序代码

AnalysisOfGrammer.java

package analysis;

import javax.swing.*;

import javax.swing.table.DefaultTableModel;

import java.awt.*;

import java.awt.event.*;

import java.io.*;

import java.util.LinkedList;

publicclass AnalysisOfGrammer extends JApplet{

private JFileChooser jfc = new JFileChooser(new File("."));

private JButton jbt1 = new JButton("打开文法文件");

private JButton jbt2 = new JButton("构造LR规范簇");

private JButton jbt3 = new JButton("构造LR分析表");

private JButton jbt4 = new JButton("清空");

private JButton jbt5 = new JButton("退出");

private JLabel jl1 = new JLabel("LR(0)项目集规范簇");

private JLabel jl2 = new JLabel("LR(0)分析表");

private JPanel p3 = new JPanel();

private JTextArea jta1 = new JTextArea();

private String[] grammer = new String[50];

privateint count = 0;

private LinkedListlist = new LinkedList();

private Object content[][] = new Object[100][4];

int num1 = 0;

String[][] cache = new String[50][100];

int[] location = newint[50];

int back = 0;

publicvoid clear1(){

grammer = null;

}

publicvoid clear2(){

num1 = 0;

list = null;

content = null;

cache = null;

location = null;

back = 0;

}

public AnalysisOfGrammer(){

JPanel p1 = new JPanel();

p1.setLayout(new GridLayout(1,5));

p1.add(jbt1);

p1.add(jbt2);

p1.add(jbt3);

p1.add(jbt4);

p1.add(jbt5);

add(p1,BorderLayout.NORTH);

JPanel p4 = new JPanel();

p4.setLayout(new GridLayout(1,2));

JPanel p2 = new JPanel();

p2.setLayout(new BorderLayout());

p2.add(new JLabel("文法为："),BorderLayout.NORTH);

p2.add(new JScrollPane(jta1),BorderLayout.CENTER);

p4.add(p2);

p4.add(p3);

add(p4,BorderLayout.CENTER);

jbt1.addActionListener(new ActionListener(){

publicvoid actionPerformed(ActionEvent e){

jta1.setText("");

open();

}

});

jbt2.addActionListener(new ActionListener(){

publicvoid actionPerformed(ActionEvent e){

if(jta1.getText().equals(""))

JOptionPane.showMessageDialog(null, "请打开文法文件！");

else{

DNF();

list.get(1).setNextState("接受态");

for(int k = 0 ; k

content[k][0] = list.get(k).getState();

content[k][1] = list.get(k).getProjectSet();

content[k][2] = list.get(k).getNextSign();

content[k][3] = list.get(k).getNextState();

}

String columnName[] = {"状态","项目集","后继符号","后继状态"};

JTable table = new JTable(content,columnName);

p3.setLayout(new BorderLayout());

p3.add(jl1,BorderLayout.NORTH);

p3.add(new JScrollPane(table),BorderLayout.CENTER);

}

clear2();

}

});

}

publicint getleng(String[] s){//获得一个字符串数组的真实长度

int len = 0;

while(s[len]!=null){

len++;

}

return len;

}

publicvoid DNF(){//自动机的构成

int c = 0;

int[] flag = newint[100];

String start = "S'-.>"+grammer[0].substring(0, 1);

flag[num1] = createI(start);//初态集建立

location[num1] = getleng(cache[num1]);

while(back<= num1){

if(c

num1++;

list.get(back).setNextState(list.get(back).getNextState()+"S"+num1+" ");

flag[num1] = createI(cache[back][c]);

location[num1] = getleng(cache[num1]);

c++;

}else{

back++;

c = 0;

}

}

}

publicint createI(String t){//生成状态集

int end = 0;

String s = addPoint(t);

String head = findNext(s);

String state = "S"+num1;;

String nextsign="";

String nextstate="";

boolean[] gra = newboolean[count];

int c = 1;

int loop = 0;

for(int k = 0 ; cache[k][0] != null; k++){

if(cache[k][0].equals(s)){

loop = k;

end = 2;

break;

}

}

if(end == 2){//更改后继状态

String old = list.get(back).getNextState();

String sta = "S"+num1;

String renew = "";

int staleng = sta.length();

for(int k = 0 ; k

if(old.substring(k,k+staleng).matches(sta)||old.equals("归约")){

num1--;

renew =

old.substring(0,k-1)+"S"+loop+old.substring(k+staleng+1, old.length())+" ";

list.get(back).setNextState(renew);

break;

}

elseif(old.equals("归约")){

num1--;

renew =

old.substring(0,k-1)+"S"+loop+old.substring(k+staleng+1, old.length())+" ";

list.get(back).setNextState(renew);

break;

}

}

return end;

}

cache[num1][0] = s;

String set = cache[num1][0] + " ";

if(num1

nextsign=list.get(num1).getNextSign();

nextstate=list.get(num1).getNextState();

set = list.get(num1).getProjectSet()+cache[num1][0] + " ";

}

if(findNext(s).equals("#")){

set = s;

nextsign = "#";

nextstate = "归约";

ViablePrefixe o = new ViablePrefixe(state,set,nextsign,nextstate);

list.add(o);

return 1;

}

else{

while(true){

int i = 0;

for(; i

if(grammer[i].substring(0,

1).equals(head)&&gra[i]!=true){

set = set + addPoint(grammer[i]) +" ";

cache[num1][c++] = addPoint(grammer[i]);

if(findNext(addPoint(grammer[i])).matches("[A-Z]")&&gra[i]!=true){

gra[i] = true;

head = findNext(addPoint(grammer[i]));

break;

}

}

}//for循环结束

if(i>= count&&head.equals(findNext(s).substring(0,1))) break;

elseif(i>= count){

head = grammer[0].substring(0,1);

}

}//while循环结束

int cc = 0; //设置下一状态的值

String[] nextS = new String[50];

for(int i = 0 ; cache[num1][i]!=null; i++){

int j = 0;

boolean f = false;

for(; nextS[j]!=null;j++){

if(findNext(cache[num1][i]).equals(nextS[j])){

f = true; break;

}

}//for j 的循环结束,查找有无相同的后继符号，f作为标记，相同的符号跳过，不同的记录下来,放在nestS[]里

if(f != true){

nextS[cc++] = findNext(cache[num1][j]);

nextsign = nextsign+findNext(cache[num1][j])+" ";

}

}//for i循环结束

ViablePrefixe o = new ViablePrefixe(state,set,nextsign,nextstate);

list.add(o);

}

return end;

}

publicint show(String s, String[] grammer){//文法的拆分函数，显示在界面上，返回值是文法的条数

boolean lastSign = false;//上一符号为\n

int flag1 = 0;//上一符号位置

int count = 0;

String str = s.substring(flag1, flag1+3);

for(int i = 0 ; i

if(s.substring(i, i+1).equals("|")){

if(lastSign)

grammer[count++] = str + s.substring(flag1, i);

else

grammer[count++] = s.substring(flag1, i);

flag1 = i + 1;

lastSign = true;

}

elseif(s.substring(i, i+1).equals("\n")){

if(lastSign)

grammer[count++] = str + s.substring(flag1, i);

else

grammer[count++] = s.substring(flag1, i);

flag1 = i+1;

if(flag1+3

str = s.substring(flag1, flag1+3);

lastSign = false;

}

elseif(s.substring(i, i+1).equals("\r")){

if(lastSign)

grammer[count++] = str + s.substring(flag1, i);

else

grammer[count++] = s.substring(flag1, i);

i++;

flag1 = i+1;

if(flag1+3

str = s.substring(flag1, flag1+3);

lastSign = false;

}

}

return count;

}

privatevoid open(){//打开文件

String s ="";

if(jfc.showOpenDialog(this) == JFileChooser.APPROVE_OPTION) s = open(jfc.getSelectedFile());

count = show(s,grammer);

for(int i = 0 ; grammer[i]!=null ; i++){

jta1.append(grammer[i]);

jta1.append("\n");

}

}

private String open(File file){//打开文件

String content1 = "";

try{

BufferedInputStream in =

new BufferedInputStream(new FileInputStream(file));

byte[] b = newbyte[in.available()];

in.read(b,0,b.length);

content1 = new String(b,0,b.length);

in.close();

}

catch(IOException ex){

jta1.setText("Error opening " + file.getName());

}

return content1;

}

privatestatic String addPoint(String m){//在文法中添加.

String t="";

int i;

for(i = 0 ; i

if(m.substring(i,i+1).equals(".")){

if(i == m.length()-1)return m;

t =

m.substring(0,i)+m.substring(i+1,i+2)+"."+m.substring(i+2,m.length());

break;

}

}

if(i>m.length()-1)

t = m.substring(0,3)+"."+m.substring(3,m.length());

return t;

}

privatestatic String findNext(String m){//返回.后的字母

String c = "#";

for(int i = 0 ; i

if(m.substring(i,i+1).equals(".")){

c= m.substring(i+1,i+2);

}

}

return c;

}

}

ViablePrefixe.java

package analysis;

publicclass ViablePrefixe {//活前缀类

private String state = "";//状态

private String projectSet = "";//项目

private String nextSign = "";//后继符号

private String nextState = "";//后继状态

public ViablePrefixe(String state,String projectSet,String nextSign,String n extState){

this.state = state;

this.projectSet = projectSet;

this.nextSign = nextSign;

this.nextState = nextState;

}

public ViablePrefixe(String state,String projectSet,String nextSign){ this.state = state;

this.projectSet = projectSet;

this.nextSign = nextSign;

}

public ViablePrefixe(String state,String projectSet){

this.state = state;

this.projectSet = projectSet;

}

public ViablePrefixe(){

}

public StringgetState() {

return state;

}

publicvoid setState(String state) {

this.state = state;

}

public StringgetProjectSet() {

return projectSet;

}

publicvoid setProjectSet(String projectSet) {

this.projectSet = projectSet;

}

public StringgetNextSign() {

return nextSign;

}

publicvoid setNextSign(String nextSign) {

this.nextSign = nextSign;

}

public StringgetNextState() {

return nextState;

}

publicvoid setNextState(String nextState) {

this.nextState = nextState;

}

public StringtoString(){

return state+" "+projectSet+" "+nextSign+" "+nextState+"\n"; }

}

三、实验结果