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This artifact contains the API of AutomataLib, which mainly consists of interfaces for the various concepts and automaton models supported by the AutomataLib core. In addition to that, it also defines some fundamental classes for dealing with words of symbols.
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/* Copyright (C) 2013 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 * 
 * AutomataLib is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 3.0 as published by the Free Software Foundation.
 * 
 * AutomataLib 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with AutomataLib; if not, see
 * http://www.gnu.de/documents/lgpl.en.html.
 */
package net.automatalib.words;

import java.util.Collections;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Objects;

/**
 * A word consisting of a single letter only.
 * 
 * @author Malte Isberner 
 *
 * @param  symbol class
 * @see Collections#singletonList(Object)
 */
final class LetterWord extends Word {
	
	/*
	 * Iterator
	 */
	private static final class Iterator implements java.util.Iterator {
		
		private final I letter;
		private boolean next = true;
		
		public Iterator(I letter) {
			this.letter = letter;
		}
		
		/*
		 * (non-Javadoc)
		 * @see java.util.Iterator#hasNext()
		 */
		@Override
		public boolean hasNext() {
			return next;
		}

		/*
		 * (non-Javadoc)
		 * @see java.util.Iterator#next()
		 */
		@Override
		public I next() {
			if(next) {
				next = false;
				return letter;
			}
			throw new NoSuchElementException();
		}

		/*
		 * (non-Javadoc)
		 * @see java.util.Iterator#remove()
		 */
		@Override
		public void remove() {
			throw new UnsupportedOperationException();
		}
		
	}
	
	private final I letter;
	
	/**
	 * Constructor.
	 * @param letter the letter to represent as a word
	 */
	public LetterWord(I letter) {
		this.letter = letter;
	}
	

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#getSymbol(int)
	 */
	@Override
	public I getSymbol(int index) {
		if(index != 0)
			throw new IndexOutOfBoundsException();
		return letter;
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#length()
	 */
	@Override
	public int length() {
		return 1;
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#subWord(int, int)
	 */
	@Override
	public Word _subWord(int fromIndex, int toIndex) {
		if(fromIndex > 0 || toIndex == 0)
			return Word.epsilon();
		return this;
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#iterator()
	 */
	@Override
	public java.util.Iterator iterator() {
		return new Iterator<>(letter);
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#writeToArray(int, java.lang.Object[], int, int)
	 */
	@Override
	public void writeToArray(int offset, Object[] array, int tgtOffset,
			int length) {
		if(offset == 0 && length > 0)
			array[tgtOffset] = letter;
	}
	
	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#lastSymbol()
	 */
	@Override
	public I lastSymbol() {
		return letter;
	}




	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#asList()
	 */
	@Override
	public List asList() {
		return Collections.singletonList(letter);
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#prepend(java.lang.Object)
	 */
	@Override
	public Word prepend(I symbol) {
		Object[] array = new Object[]{symbol, letter};
		return new SharedWord<>(array);
	}
	
	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#append(java.lang.Object)
	 */
	@Override
	public Word append(I symbol) {
		Object[] array = new Object[]{letter, symbol};
		return new SharedWord<>(array);
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#isPrefixOf(net.automatalib.words.Word)
	 */
	@Override
	public boolean isPrefixOf(Word other) {
		if(other.length() == 0)
			return false;
		return Objects.equals(letter, other.getSymbol(0));
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#longestCommonPrefix(net.automatalib.words.Word)
	 */
	@Override
	public Word longestCommonPrefix(Word other) {
		if(isPrefixOf(other))
			return this;
		return Word.epsilon();
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#isSuffixOf(net.automatalib.words.Word)
	 */
	@Override
	public boolean isSuffixOf(Word other) {
		if(other.isEmpty())
			return false;
		return Objects.equals(letter, other.lastSymbol());
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#longestCommonSuffix(net.automatalib.words.Word)
	 */
	@Override
	public Word longestCommonSuffix(Word other) {
		if(isSuffixOf(other))
			return this;
		return Word.epsilon();
	}
	
	
	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#flatten()
	 */
	@Override
	public Word flatten() {
		return this;
	}


	/* (non-Javadoc)
	 * @see net.automatalib.words.Word#trimmed()
	 */
	@Override
	public Word trimmed() {
		return this;
	}
	
	
}