Java implementation eliminates left recursion of grammar

Tag:java    compiler principle     eliminate left recursive    

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;} @Overridepublic  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 ();        //-Generation Private list  symbols = new arraylist ();         // Initial production non-Terminator private list nonterminatingsymbol = new arraylist ();  //ll (1) Grammar non-Terminator private list terminatingsymbol = new arraylist ();     //ll (1 ) grammar Terminator 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 ();   (_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")));}}} @Overridepublic  string tostring ()  {String temp =  "non-Terminator: ";for  (int  i = 0; i < nonterminatingsymbol.size ();  i++)  {temp +=  Nonterminatingsymbol.get (i)  +  " ";} temp+= "   total:" +nonterminatingsymbol.size ();temp +=  "\\n Terminator: ";for  (int i  = 0; i < terminatingsymbol.size ();  i++)  {temp +=  Terminatingsymbol.get (i)  +  "  ";} temp+= "   total:" +terminatingsymbol.size ();temp +=  "\\n Eliminate left recursion grammar: \\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");}}

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Java implementation eliminates left recursion of grammar