算符优先分析表生成模拟

来源：互联网发布：电影大全软件编辑：程序博客网时间：2024/06/14 10:14

【问题描述】

设计一个给定文法和对应的FIRSTVT和LASTVT集，能依据依据文法和FIRSTVT和LASTVT生成算符优先分析表。

import java.util.ArrayList;
import java.util.Iterator;

public class OP {

public ArrayList<Production> production = new ArrayList<Production>();// 存储产生式
String[] vn;
String[] vt;
int[][] FstTable; // FirstVT表
int[][] LstTable; // LastVT表
int[][] PriorTable; // 优先级表

public void input() {

  production.add(new Production("B", "BoT"));
  production.add(new Production("B", "T"));
  production.add(new Production("T", "TaF"));
  production.add(new Production("T", "F"));
  production.add(new Production("F", "nF"));
  production.add(new Production("F", "(B)"));
  production.add(new Production("F", "t"));
  production.add(new Production("F", "f"));

  /* 初始化非终结字符集 */
  vn = new String[3];
  vn[0] = "B";
  vn[1] = "T";
  vn[2] = "F";

  /* 初始化终结字符集 */
  vt = new String[7];
  vt[0] = "o";
  vt[1] = "a";
  vt[2] = "n";
  vt[3] = "(";
  vt[4] = ")";
  vt[5] = "t";
  vt[6] = "f";

  FstTable = new int[vn.length][vt.length];
  LstTable = new int[vn.length][vt.length];
  PriorTable = new int[vt.length][vt.length];
  /* B的Firstvt */
  FstTable[0][0] = 1;
  FstTable[0][1] = 1;
  FstTable[0][2] = 1;
  FstTable[0][3] = 1;
  FstTable[0][4] = 0;
  FstTable[0][5] = 1;
  FstTable[0][6] = 1;

  /* T的Firstvt */
  FstTable[1][0] = 0;
  FstTable[1][1] = 1;
  FstTable[1][2] = 1;
  FstTable[1][3] = 1;
  FstTable[1][4] = 0;
  FstTable[1][5] = 1;
  FstTable[1][6] = 1;
  /* F的Firstvt */
  FstTable[2][0] = 0;
  FstTable[2][1] = 0;
  FstTable[2][2] = 1;
  FstTable[2][3] = 1;
  FstTable[2][4] = 0;
  FstTable[2][5] = 1;
  FstTable[2][6] = 1;

  /* B的Lastvt */
  LstTable[0][0] = 1;
  LstTable[0][1] = 1;
  LstTable[0][2] = 1;
  LstTable[0][3] = 0;
  LstTable[0][4] = 1;
  LstTable[0][5] = 1;
  LstTable[0][6] = 1;

  /* T的Lastvt */
  LstTable[1][0] = 0;
  LstTable[1][1] = 1;
  LstTable[1][2] = 1;
  LstTable[1][3] = 0;
  LstTable[1][4] = 1;
  LstTable[1][5] = 1;
  LstTable[1][6] = 1;

  /* F的Lastvt */
  LstTable[2][0] = 0;
  LstTable[2][1] = 0;
  LstTable[2][2] = 1;
  LstTable[2][3] = 0;
  LstTable[2][4] = 1;
  LstTable[2][5] = 1;
  LstTable[2][6] = 1;

}

/* 判断是否为终结符 */
public boolean isVT(String str) {
  boolean bool = false;
  for (int i = 0; i < vt.length; i++) {
   if (str.equals(vt[i])) {
    bool = true;
   }
  }
  return bool;
}

/* 判断是否为非终结符 */
public boolean isVN(String str) {
  boolean bool = false;
  for (int i = 0; i < vn.length; i++) {
   if (str.equals(vn[i])) {
    bool = true;
   }
  }
  return bool;
}

/* 获取某字符在终结字符数组的索引 */
public int getVTIndex(String str) {
  int index = -1;
  for (int i = 0; i < vt.length; i++) {
   if (str.equals(vt[i])) {
    index = i;
   }
  }
  return index;
}

/* 获取某字符在终结字符数组的索引 */
public int getVNIndex(String str) {
  int index = -1;
  for (int i = 0; i < vn.length; i++) {
   if (str.equals(vn[i])) {
    index = i;
   }
  }
  return index;
}

public void p(String str) {
  System.out.print(str);
}

public void showProduction(){
  p("*****以下显示的是您输入的产生式*****/n");
  Iterator iterator = production.iterator();
  while (iterator.hasNext()) {
   Production pro = (Production) iterator.next();
      System.out.println(pro.left+"->"+pro.right);
  }
}

/*显示输入的FIRSTVT集*/
public void showFst(){
  p("*****以下显示的是您输入的FIRSTVT集*****/n");
  p(" ");
  for (int i = 0; i < vt.length; i++) {
   p(" " + vt[i]);
  }
  for(int i=0;i<FstTable.length;i++){
   p("/n" + vn[i]);
   for(int j=0;j<FstTable[i].length;j++){
    if (FstTable[i][j] == 0)
     p("   ");
    if (FstTable[i][j] == 1)
     p(" 1");
   }
  }
}

/*显示输入的LASTVT集*/
public void showLst(){
  p("/n*****以下显示的是您输入的LASTVT集*****/n");
  p(" ");
  for (int i = 0; i < vt.length; i++) {
   p(" " + vt[i]);
  }
  for(int i=0;i<LstTable.length;i++){
   p("/n" + vn[i]);
   for(int j=0;j<LstTable[i].length;j++){
    if (LstTable[i][j] == 0)
     p("   ");
    if (LstTable[i][j] == 1)
     p(" 1");
   }
  }
}

/* 构造文法的优先关系表 */
public void ShowPriorTalbe() {
Iterator iterator = production.iterator();

  while (iterator.hasNext()) {
   Production pro = (Production) iterator.next();
   /* 对产生式的右部进行遍历 */
   for (int i = 0; i < pro.right.length() - 1; i++) {
    /* 获取产生式右部的第i个和第i+1个字符 */
    String ch = String.valueOf(pro.right.charAt(i));
    String ch1 = String.valueOf(pro.right.charAt(i + 1));
    /* 获得该终结符在终结符集的索引 */
    int VTindex = getVTIndex(ch);
    int VTindex1 = getVTIndex(ch1);
    /* 获得该终结符在非终结符集的索引 */
    int VNindex = getVNIndex(ch);
    int VNindex1 = getVNIndex(ch1);

    /*IF X(i)和X(i+1)均为终结符*/
    if (isVT(ch) && isVT(ch1)) {
     // x(i)=x(i+1)
     if (VTindex == -1 || VTindex1 == -1) {
      System.out.println("该字符不在终结字符集内");
     } else {
      PriorTable[VTindex][VTindex1] = 2;// 标记 "="
     }
    }

    /*IF i<=n-2 且X(i)和X(i+2)都为终结符,但X(i+1)为非终结符*/
    if (i < pro.right.length() - 2 && isVT(ch)
      && isVT(String.valueOf(pro.right.charAt(i + 2)))
      && isVN(ch1)) {
     // xi = x(i+2)
     int prior2 = getVTIndex(String.valueOf(pro.right
       .charAt(i + 2)));
     if (VTindex == -1 || prior2 == -1) {
      System.out.println("该字符不在终结字符集内");
     } else {
      PriorTable[VTindex][prior2] = 2;// 标记 "="
     }
    }

    /*IF X(i)为终结符而X(i+1)为非终结符
     * THEN FOR FIRSTVT(X(i+1)) 中的每个 b DO 置 X(i)<b;
     * */
    if (isVT(ch) && isVN(ch1)) {
     // x(i)<b
     for (int j = 0; j < FstTable[VNindex1].length; j++) {
      if (FstTable[VNindex1][j] == 1) {
       PriorTable[VTindex][j] = 1;// 标记 "<"
      }
     }
    }

    /*IF X(i)为非终结符而X(i+1)为终结符
     * THEN FOR LASTVT(X(i)中的每个a DO 置a>X(i+1);
     * */
    if (isVN(ch) && isVT(ch1)) {
     // a>x(i+1)
     for (int j = 0; j < LstTable[VNindex].length; j++) {
      if (LstTable[VNindex][j] == 1) {
       PriorTable[j][VTindex1] = 3; // 标记 ">"
      }
     }
    }
   }
  }
}

/* 根据二维数组显示输出优先关系分析表 */
public void output() {
  p("/n*****以下显示的是构造出来的优先关系表*****/n");
  p(" ");
  for (int i = 0; i < vt.length; i++) {
   p(" " + vt[i]);
  }

  for (int i = 0; i < PriorTable.length; i++) {
   try {
    Thread.sleep(1000);
   } catch (InterruptedException e) {
    e.printStackTrace();
   }
   p("/n" + vt[i]);
   for (int j = 0; j < PriorTable[i].length; j++) {
    if (PriorTable[i][j] == 0)
     p("   ");
    if (PriorTable[i][j] == 1)
     p(" <");
    if (PriorTable[i][j] == 2)
     p(" =");
    if (PriorTable[i][j] == 3)
     p(" >");
   }
  }
}

public static void main(String[] args) {

  OP op = new OP();
  op.input();
  op.showProduction();
  op.showFst();
  op.showLst();
  op.ShowPriorTalbe();
  op.output();
}

}

/* 产生式结构 */
class Production {

public String left;
public String right;

public Production(String left, String right) {
this.left = left;
this.right = right;
}
}