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      1 /*
      2  * [The "BSD license"]
      3  *  Copyright (c) 2010 Terence Parr
      4  *  All rights reserved.
      5  *
      6  *  Redistribution and use in source and binary forms, with or without
      7  *  modification, are permitted provided that the following conditions
      8  *  are met:
      9  *  1. Redistributions of source code must retain the above copyright
     10  *      notice, this list of conditions and the following disclaimer.
     11  *  2. Redistributions in binary form must reproduce the above copyright
     12  *      notice, this list of conditions and the following disclaimer in the
     13  *      documentation and/or other materials provided with the distribution.
     14  *  3. The name of the author may not be used to endorse or promote products
     15  *      derived from this software without specific prior written permission.
     16  *
     17  *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     18  *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     19  *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     20  *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     21  *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     22  *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     23  *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     24  *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25  *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     26  *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 package org.antlr.analysis;
     29 
     30 import org.antlr.misc.IntSet;
     31 import org.antlr.misc.IntervalSet;
     32 import org.antlr.tool.Grammar;
     33 
     34 /** An LL(1) lookahead set; contains a set of token types and a "hasEOF"
     35  *  condition when the set contains EOF.  Since EOF is -1 everywhere and -1
     36  *  cannot be stored in my BitSet, I set a condition here.  There may be other
     37  *  reasons in the future to abstract a LookaheadSet over a raw BitSet.
     38  */
     39 public class LookaheadSet {
     40 	public IntervalSet tokenTypeSet;
     41 
     42 	public LookaheadSet() {
     43 		tokenTypeSet = new IntervalSet();
     44 	}
     45 
     46 	public LookaheadSet(IntSet s) {
     47 		this();
     48 		tokenTypeSet.addAll(s);
     49 	}
     50 
     51 	public LookaheadSet(int atom) {
     52 		tokenTypeSet = IntervalSet.of(atom);
     53 	}
     54 
     55     public LookaheadSet(LookaheadSet other) {
     56         this();
     57         this.tokenTypeSet.addAll(other.tokenTypeSet);
     58     }
     59 
     60     public void orInPlace(LookaheadSet other) {
     61 		this.tokenTypeSet.addAll(other.tokenTypeSet);
     62 	}
     63 
     64 	public LookaheadSet or(LookaheadSet other) {
     65 		return new LookaheadSet(tokenTypeSet.or(other.tokenTypeSet));
     66 	}
     67 
     68 	public LookaheadSet subtract(LookaheadSet other) {
     69 		return new LookaheadSet(this.tokenTypeSet.subtract(other.tokenTypeSet));
     70 	}
     71 
     72 	public boolean member(int a) {
     73 		return tokenTypeSet.member(a);
     74 	}
     75 
     76 	public LookaheadSet intersection(LookaheadSet s) {
     77 		IntSet i = this.tokenTypeSet.and(s.tokenTypeSet);
     78 		LookaheadSet intersection = new LookaheadSet(i);
     79 		return intersection;
     80 	}
     81 
     82 	public boolean isNil() {
     83 		return tokenTypeSet.isNil();
     84 	}
     85 
     86 	public void remove(int a) {
     87 		tokenTypeSet = (IntervalSet)tokenTypeSet.subtract(IntervalSet.of(a));
     88 	}
     89 
     90 	public int hashCode() {
     91 		return tokenTypeSet.hashCode();
     92 	}
     93 
     94 	public boolean equals(Object other) {
     95 		return tokenTypeSet.equals(((LookaheadSet)other).tokenTypeSet);
     96 	}
     97 
     98 	public String toString(Grammar g) {
     99 		if ( tokenTypeSet==null ) {
    100 			return "";
    101 		}
    102 		String r = tokenTypeSet.toString(g);
    103 		return r;
    104 	}
    105 
    106 	public String toString() {
    107 		return toString(null);
    108 	}
    109 }
    110