001/* Copyright (C) 2013 TU Dortmund
002 * This file is part of AutomataLib, http://www.automatalib.net/.
003 * 
004 * AutomataLib is free software; you can redistribute it and/or
005 * modify it under the terms of the GNU Lesser General Public
006 * License version 3.0 as published by the Free Software Foundation.
007 * 
008 * AutomataLib is distributed in the hope that it will be useful,
009 * but WITHOUT ANY WARRANTY; without even the implied warranty of
010 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
011 * Lesser General Public License for more details.
012 * 
013 * You should have received a copy of the GNU Lesser General Public
014 * License along with AutomataLib; if not, see
015 * http://www.gnu.de/documents/lgpl.en.html.
016 */
017package net.automatalib.words;
018
019
020/**
021 * {@link Alphabet} class that supports adding new symbols.
022 * 
023 * @param <I> symbol class.
024 * 
025 * @author Malte Isberner <malte.isberner@gmail.com>
026 */
027public interface GrowingAlphabet<I> extends Alphabet<I> {
028
029    /**
030     * Adds a new symbol to the alphabet. Some alphabets may prevent
031     * symbols from being added twice. In this case, the original alphabet
032     * remains unchanged, but this is not considered an error.
033     *
034     * @return the index of the symbol in the alphabet, after adding it.
035     */
036    public abstract int addSymbol(I a);
037    
038}