LR1Item.java

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * This file is part of SableCC.                             *
 * See the file "LICENSE" for copyright information and the  *
 * terms and conditions for copying, distribution and        *
 * modification of SableCC.                                  *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

package org.sablecc.sablecc;


@SuppressWarnings("rawtypes")
final class LR1Item implements Cloneable, Comparable {
    final LR0Item lr0Item;
    final int terminal;

    LR1Item(LR0Item lr0Item, int terminal) {
        this.lr0Item = lr0Item;
        this.terminal = terminal;
    }

    @Override
    public Object clone() {
        return new LR1Item(lr0Item, terminal);
    }

    @Override
    public boolean equals(Object obj) {
        if ((obj == null) ||
                (obj.getClass() != this.getClass())) {
            return false;
        }

        LR1Item item = (LR1Item) obj;

        return (item.lr0Item.equals(lr0Item)) &&
                (item.terminal == terminal);
    }

    @Override
    public int hashCode() {
        return lr0Item.hashCode() * (terminal + 1) * 37;
    }

    @Override
    public String toString() {
        return lr0Item + ":" + Symbol.symbol(terminal, true);
    }

    public String toString(Symbol lookahead) {
        // two cases:
        // (1) we are facing a reduction, and the lookahed
        //     should match
        // (2) we are in the middle of a production.  The
        //     next element should match.

        Symbol[] rightside = Production.production(lr0Item.production).rightside();

        if (lr0Item.position == rightside.length) {
            Symbol term = Symbol.symbol(terminal, true);

            if (term == lookahead) {
                return lr0Item + " followed by " + term + " (reduce)";
            } else {
                return null;
            }
        }

        if (rightside[lr0Item.position] == lookahead) {
            return lr0Item + " (shift)";
        } else {
            return null;
        }
    }

    @Override
    public int compareTo(Object object) {
        LR1Item item = (LR1Item) object;

        int result = lr0Item.compareTo(item.lr0Item);

        if (result == 0) {
            result = terminal - item.terminal;
        }

        return result;
    }
}