AbstractPLVisitor.java

package aima.core.logic.propositional.parsing;

import aima.core.logic.propositional.parsing.ast.ComplexSentence;
import aima.core.logic.propositional.parsing.ast.Sentence;
import aima.core.logic.propositional.parsing.ast.PropositionSymbol;

/**
 * Abstract implementation of the PLVisitor interface that provides default
 * behavior for each of the methods.
 * 
 * @author Ravi Mohan
 * @author Ciaran O'Reilly
 * 
 * @param <A>
 *            the argument type to be passed to the visitor methods.
 */
public abstract class AbstractPLVisitor<A> implements PLVisitor<A, Sentence> {

	@Override
	public Sentence visitPropositionSymbol(PropositionSymbol s, A arg) {
		// default behavior is to treat propositional symbols as atomic
		// and leave unchanged.
		return s;
	}

	@Override
	public Sentence visitUnarySentence(ComplexSentence s, A arg) {
		// a new Complex Sentence with the same connective but possibly
		// with its simpler sentence replaced by the visitor.
		return new ComplexSentence(s.getConnective(), s.getSimplerSentence(0)
				.accept(this, arg));
	}

	@Override
	public Sentence visitBinarySentence(ComplexSentence s, A arg) {
		// a new Complex Sentence with the same connective but possibly
		// with its simpler sentences replaced by the visitor.
		return new ComplexSentence(s.getConnective(), s.getSimplerSentence(0)
				.accept(this, arg), s.getSimplerSentence(1).accept(this, arg));
	}
}