/*******************************************************************************
* Copyright (c) 2009-2013 CWI
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* * Jurgen J. Vinju - Jurgen.Vinju@cwi.nl - CWI
* * Emilie Balland - (CWI)
* * Arnold Lankamp - Arnold.Lankamp@cwi.nl
*******************************************************************************/
package org.rascalmpl.interpreter.matching;
import org.rascalmpl.interpreter.IEvaluatorContext;
import org.rascalmpl.interpreter.env.Environment;
/**
* The equivalence boolean operator backtracks for both the lhs and the rhs. This means
* that if the lhs or rhs have multiple ways of assigning a value to a variable,
* this and operator will be evaluated as many times.
*/
public class EquivalenceResult extends AbstractBooleanResult {
private final IBooleanResult left;
private final IBooleanResult right;
private boolean firstMatch = true;
private boolean leftResult;
public EquivalenceResult(IEvaluatorContext ctx, IBooleanResult left, IBooleanResult right) {
super(ctx);
this.left = left;
this.right = right;
}
@Override
public void init() {
super.init();
left.init();
right.init();
firstMatch = true;
leftResult = false;
}
public boolean hasNext() {
if (firstMatch) {
return left.hasNext() && right.hasNext();
}
return right.hasNext() || left.hasNext();
}
@Override
public boolean next() {
if (firstMatch) {
firstMatch = false;
Environment old = ctx.getCurrentEnvt();
boolean rightResult;
try {
ctx.pushEnv();
leftResult = left.next();
}
finally {
ctx.unwind(old);
}
try {
ctx.pushEnv();
rightResult = right.next();
}
finally {
ctx.unwind(old);
}
return leftResult == rightResult;
}
if (right.hasNext()) {
Environment old = ctx.getCurrentEnvt();
try {
ctx.pushEnv();
return leftResult == right.next();
}
finally {
ctx.unwind(old);
}
}
Environment old = ctx.getCurrentEnvt();
try {
ctx.pushEnv();
leftResult = left.next();
}
finally {
ctx.unwind(old);
}
try {
right.init();
return leftResult == right.next();
}
finally {
ctx.unwind(old);
}
}
}