package com.siwanghu.syntaxanalyzer.bean; public class Grammar { private String left; private String right; private int id; private static int ID = 0; public Grammar() { super(); id = ID++; } public Grammar(String left, String right) { super(); this.left = left; this.right = right; id = ID++; } public String getLeft() { return left; } public void setLeft(String left) { this.left = left.replace(" ", ""); } public String getRight() { return right; } public void setRight(String right) { this.right = right.replace(" ", ""); } public int getId() { return id; } @Override public String toString() { return "Grammar [left=" + left + ", right=" + right + "]"; } }
package com.siwanghu.syntaxanalyzer.algorithm; import java.util.ArrayList; import java.util.LinkedList; import java.util.List; import java.util.ListIterator; import com.siwanghu.syntaxanalyzer.bean.Grammar; public class Production { private List productions = new LinkedList(); //产生式 private List symbols = new ArrayList(); //初始产生式非终结符 private List nonTerminatingSymbol = new ArrayList(); //LL(1)文法非终结符 private List terminatingSymbol = new ArrayList(); //LL(1)文法终结符 public Production(List productions) { super(); this.productions = productions; symbolProductions(); } public List getProductions() { return productions; } public List getSymbols() { return symbols; } public List getNonTerminatingSymbol(){ return nonTerminatingSymbol; } public List getTerminatingSymbol(){ return terminatingSymbol; } public void removeLeftRecursion() { for (int i = 0; i < symbols.size(); i++) { for (int j = 0; j < i; j++) { iterativeReplacement(symbols.get(i), symbols.get(j)); } removeLeftRecursion(symbols.get(i)); } no_or_is_terminatingSymbol(); } private void symbolProductions() { if (productions.size() != 0) { for (int i = 0; i < productions.size(); i++) { if (!((ArrayList) symbols).contains(productions .get(i).getLeft().charAt(0))) { symbols.add(productions.get(i).getLeft().charAt(0)); } } } } private void no_or_is_terminatingSymbol() { for (int i = 0; i < productions.size(); i++) { if (!((ArrayList) nonTerminatingSymbol) .contains(productions.get(i).getLeft())) { nonTerminatingSymbol.add(productions.get(i).getLeft()); } if (productions.get(i).getLeft() == productions.get(i).getLeft() .charAt(0) + "‘") { nonTerminatingSymbol.add(productions.get(i).getLeft()); } } for (int i = 0; i < productions.size(); i++) { String temp = productions.get(i).getRight(); temp = temp.replace("epsilon", "#"); for (int j = 0; j < nonTerminatingSymbol.size(); j++) { temp = temp.replaceAll(nonTerminatingSymbol.get(j), ""); } temp = temp.replaceAll("\\\\|", ""); temp = temp.replaceAll("‘", ""); char[] chars = temp.toCharArray(); for (int k = 0; k < chars.length; k++) { if (chars[k] == ‘#‘) { if (!terminatingSymbol.contains("epsilon")) { terminatingSymbol.add("epsilon"); } } else { if (!terminatingSymbol.contains(String.valueOf(chars[k]))) { terminatingSymbol.add(String.valueOf(chars[k])); } } } } } private void iterativeReplacement(Character left, Character right) { ListIterator listIterator = productions.listIterator(); while (listIterator.hasNext()) { String inRight = ""; Grammar grammar = listIterator.next(); if (grammar.getLeft().equals(left.toString())) { boolean isReplacement = false; String[] rights = grammar.getRight().split("\\\\|"); for (int i = 0; i < rights.length; i++) { if (rights[i].startsWith(right.toString())) { isReplacement = true; } } if (isReplacement) { ListIterator _listIterator = productions .listIterator(); while (_listIterator.hasNext()) { Grammar _grammar = _listIterator.next(); if (_grammar.getLeft().equals(right.toString())) { String[] _rights = _grammar.getRight().split("\\\\|"); for (int i = 0; i < rights.length; i++) { boolean isCheck = false; if (rights[i].startsWith(right.toString())) { isCheck = true; for (int j = 0; j < _rights.length; j++) { String temp = rights[i]; inRight += (temp.replaceFirst( right.toString(), _rights[j]) + "|"); } } if (!isCheck) { inRight += (rights[i] + "|"); } } } } if (inRight.length() != 0) { listIterator.remove(); listIterator.add(new Grammar(left.toString(), inRight .substring(0, inRight.length() - 1))); } } } } } private void removeLeftRecursion(Character left) { ListIterator listIterator = productions.listIterator(); while (listIterator.hasNext()) { Grammar grammar = listIterator.next(); if (grammar.getLeft().equals(left.toString())) { String[] rights = grammar.getRight().split("\\\\|"); boolean isLeftRecursion = false; for (int i = 0; i < rights.length; i++) { if (rights[i].startsWith(left.toString())) { isLeftRecursion = true; } } if (isLeftRecursion) { listIterator.remove(); String oneRight = "", twoRight = ""; for (int i = 0; i < rights.length; i++) { if (!rights[i].startsWith(left.toString())) { oneRight += (rights[i] .concat(left.toString() + "‘") + "|"); } else { twoRight += (rights[i].replaceFirst( left.toString(), "").concat( left.toString() + "‘") + "|"); } } listIterator.add(new Grammar(left.toString(), oneRight .substring(0, oneRight.length() - 1))); listIterator.add(new Grammar(left.toString() + "‘", twoRight.concat("epsilon"))); } } } } @Override public String toString() { String temp = "非终结符: "; for (int i = 0; i < nonTerminatingSymbol.size(); i++) { temp += nonTerminatingSymbol.get(i) + " "; } temp+=" 共计:"+nonTerminatingSymbol.size(); temp += "\\n终结符: "; for (int i = 0; i < terminatingSymbol.size(); i++) { temp += terminatingSymbol.get(i) + " "; } temp+=" 共计:"+terminatingSymbol.size(); temp += "\\n消除左递归后的文法:\\n"; for (int i = 0; i < productions.size(); i++) { temp += (productions.get(i) + "\\n"); } return temp; } } package com.siwanghu.syntaxanalyzer.test; import java.util.LinkedList; import java.util.List; import com.siwanghu.syntaxanalyzer.algorithm.Production; import com.siwanghu.syntaxanalyzer.bean.Grammar; public class Test { public static void main(String[] args) { System.out.println("The Productions of G"); Grammar g1 = new Grammar("S", "Qc|c"); Grammar g2 = new Grammar("Q", "Rb|b"); Grammar g3 = new Grammar("R", "Sa|a"); List g_productions = new LinkedList(); g_productions.add(g3); g_productions.add(g2); g_productions.add(g1); Production g_production = new Production(g_productions); g_production.removeLeftRecursion(); System.out.print(g_production); System.out.println("end G\\n"); System.out.println("The Productions of H"); Grammar h1 = new Grammar("E", "E+T|T"); Grammar h2 = new Grammar("T", "T*F|F"); Grammar h3 = new Grammar("F", "(E)|i"); List h_productions = new LinkedList(); h_productions.add(h1); h_productions.add(h2); h_productions.add(h3); Production h_production = new Production(h_productions); h_production.removeLeftRecursion(); System.out.print(h_production); System.out.println("end H"); } }
时间: 2024-10-22 14:25:42