tool/src/main/java/org/antlr/analysis/LookaheadSet.java

/*
 * [The "BSD license"]
 *  Copyright (c) 2010 Terence Parr
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *  1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *      derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.antlr.analysis;

import org.antlr.misc.IntSet;
import org.antlr.misc.IntervalSet;
import org.antlr.tool.Grammar;

/** An LL(1) lookahead set; contains a set of token types and a "hasEOF"
 *  condition when the set contains EOF.  Since EOF is -1 everywhere and -1
 *  cannot be stored in my BitSet, I set a condition here.  There may be other
 *  reasons in the future to abstract a LookaheadSet over a raw BitSet.
 */
public class LookaheadSet {
	public IntervalSet tokenTypeSet;

	public LookaheadSet() {
		tokenTypeSet = new IntervalSet();
	}

	public LookaheadSet(IntSet s) {
		this();
		tokenTypeSet.addAll(s);
	}

	public LookaheadSet(int atom) {
		tokenTypeSet = IntervalSet.of(atom);
	}

    public LookaheadSet(LookaheadSet other) {
        this();
        this.tokenTypeSet.addAll(other.tokenTypeSet);
    }

    public void orInPlace(LookaheadSet other) {
		this.tokenTypeSet.addAll(other.tokenTypeSet);
	}

	public LookaheadSet or(LookaheadSet other) {
		return new LookaheadSet(tokenTypeSet.or(other.tokenTypeSet));
	}

	public LookaheadSet subtract(LookaheadSet other) {
		return new LookaheadSet(this.tokenTypeSet.subtract(other.tokenTypeSet));
	}

	public boolean member(int a) {
		return tokenTypeSet.member(a);
	}

	public LookaheadSet intersection(LookaheadSet s) {
		IntSet i = this.tokenTypeSet.and(s.tokenTypeSet);
		LookaheadSet intersection = new LookaheadSet(i);
		return intersection;
	}

	public boolean isNil() {
		return tokenTypeSet.isNil();
	}

	public void remove(int a) {
		tokenTypeSet = tokenTypeSet.subtract(IntervalSet.of(a));
	}

	@Override
	public int hashCode() {
		return tokenTypeSet.hashCode();
	}

	@Override
	public boolean equals(Object other) {
		return tokenTypeSet.equals(((LookaheadSet)other).tokenTypeSet);
	}

	public String toString(Grammar g) {
		if ( tokenTypeSet==null ) {
			return "";
		}
		String r = tokenTypeSet.toString(g);
		return r;
	}

	@Override
	public String toString() {
		return toString(null);
	}
}