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A collection of basic algorithm for approximating equivalence queries

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/* Copyright (C) 2013 TU Dortmund
 * This file is part of LearnLib, http://www.learnlib.de/.
 * 
 * LearnLib 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.
 * 
 * LearnLib 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 LearnLib; if not, see
 * .
 */
package de.learnlib.eqtests.basic.mealy;

import java.util.Collection;
import java.util.Objects;

import net.automatalib.automata.concepts.SODetOutputAutomaton;
import net.automatalib.words.Word;
import de.learnlib.api.EquivalenceOracle;
import de.learnlib.oracles.DefaultQuery;

public class SymbolEQOracleWrapper>, I, O> implements
		EquivalenceOracle {
	
	private final EquivalenceOracle> wordEqOracle;

	public SymbolEQOracleWrapper(EquivalenceOracle> wordEqOracle) {
		this.wordEqOracle = wordEqOracle;
	}
	
	/*
	 * (non-Javadoc)
	 * @see de.learnlib.api.EquivalenceOracle#findCounterExample(java.lang.Object, net.automatalib.words.Alphabet)
	 */
	@Override
	public DefaultQuery findCounterExample(A hypothesis, Collection inputs) {
		DefaultQuery> wordCeQry = wordEqOracle.findCounterExample(hypothesis, inputs);
		if(wordCeQry == null)
			return null;
		
		Word hypOut = hypothesis.computeSuffixOutput(wordCeQry.getPrefix(), wordCeQry.getSuffix());
		Word ceOut = wordCeQry.getOutput();
		
		
		int len = hypOut.length();
		if(len != ceOut.length())
			throw new IllegalStateException("Output word length does not align with suffix length, truncating CE will not work");
		
		

		for(int i = 0; i < len; i++) {
			O hypSym = hypOut.getSymbol(i), ceSym = ceOut.getSymbol(i);
			
			if(!Objects.equals(hypSym, ceSym)) {
				DefaultQuery result = new DefaultQuery(wordCeQry.getPrefix(),
						wordCeQry.getSuffix().prefix(i+1));
				result.answer(ceSym);
				return result;
			}
		}
		
		throw new IllegalStateException("Counterexample returned by underlying EQ oracle was none");
	}

}