org.vesalainen.grammar.state.State Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of lpg Show documentation

Java Lookahead Parser Generator. Generator produces LALR(k) parsers. Grammar rules are entered using annotations. Rule annotation can be attached to reducer method, which keeps rule and it's action together.

The newest version!

/*
 * Copyright (C) 2012 Timo Vesalainen
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.vesalainen.grammar.state;

import org.vesalainen.parser.util.Numerable;

/**
 * A base class for NFAState and DFAState
 * @author tkv
 */
public class State implements Numerable
{
    protected Scope scope;
    protected int number;
    private T token;
    private int priority;   // used to set acceptance priorities. E.g 'xml' could have higher priority than [a-z]+

    public State(Scope scope)
    {
        this.scope = scope;
        this.number = scope.next();
    }

    /**
     * Copy constructor
     * @param other
     */
    protected State(Scope scope, State other)
    {
        this.scope = scope;
        this.number = scope.next();
        token = other.token;
    }

    int getPriority()
    {
        return priority;
    }

    public void setPriority(int priority)
    {
        this.priority = priority;
    }
    
    /**
     * Changes priority. priority += change.
     * @param change 
     */
    public void changePriority(int change)
    {
        priority += change;
    }
    /**
     * Returns true if this state is accepting.
     * @return
     */
    public boolean isAccepting()
    {
        return token != null;
    }
    /**
     * Return the reducer value
     * @return
     */
    public T getToken()
    {
        return token;
    }
    /**
     * Sets the reducer value
     * @param token
     */
    public void setToken(T token)
    {
        if (token == null)
        {
            throw new IllegalArgumentException("setting null token is illegal");
        }
        this.token = token;
    }

    @Override
    public String toString()
    {
        if (token == null)
        {
            return "S"+number;
        }
        else
        {
            return "S("+number+")";
        }
    }
    @Override
    public int hashCode()
    {
        return number;
    }

    public boolean equals(Object obj)
    {
        if (obj == null)
        {
            return false;
        }
        if (getClass() != obj.getClass())
        {
            return false;
        }
        final State other = (State) obj;
        if (this.scope != other.scope)
        {
            throw new IllegalArgumentException("testing equality of States from different scope");
        }
        if (this.number != other.number)
        {
            return false;
        }
        return true;
    }

    public int getNumber()
    {
        return number;
    }

    public Scope getScope()
    {
        return scope;
    }


}