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/*******************************************************************************
* Copyright (c) 2004-2010 Gabor Bergmann and Daniel Varro
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-v20.html.
*
* SPDX-License-Identifier: EPL-2.0
*******************************************************************************/
package tools.refinery.viatra.runtime.matchers.psystem;
import java.util.HashSet;
import java.util.Set;
/**
* @author Gabor Bergmann
*
*/
public class PVariable {
private PBody pBody;
/**
* The name of the pattern variable. This is the unique key of the pattern node.
*/
private String name;
/**
* virtual pVariables are nodes that do not correspond to actual pattern variables; they represent constants or Term
* substitutes
*/
private boolean virtual;
/**
* Set of constraints that mention this variable
*/
private Set<PConstraint> referringConstraints;
/**
* Determines whether there are any constraints that can deduce this variable
*/
private Boolean deducable;
/**
* Another PVariable this variable has been unified into. Please use the other variable instead of this. Null iff
* this is still a first-class variable.
*/
private PVariable unifiedInto;
PVariable(PBody pBody, String name) {
this(pBody, name, false);
}
PVariable(PBody pBody, String name, boolean virtual) {
super();
this.pBody = pBody;
this.name = name;
this.virtual = virtual;
// this.exportedParameter = false;
this.referringConstraints = new HashSet<PConstraint>();
this.unifiedInto = null;
this.deducable = false;
}
/**
* Replaces this variable with a given other, resulting in their unification. This variable will no longer be
* unique.
*
* @param replacement
*/
public void unifyInto(PVariable replacement) {
pBody.checkMutability();
replacementCheck();
replacement = replacement.getUnifiedIntoRoot();
if (this.equals(replacement))
return;
if (!this.isVirtual() && replacement.isVirtual()) {
replacement.unifyInto(this);
} else {
// replacement.referringConstraints.addAll(this.referringConstraints);
// replacement.exportedParameter |= this.exportedParameter;
replacement.virtual &= this.virtual;
if (replacement.deducable != null && this.deducable != null)
replacement.deducable |= this.deducable;
else
replacement.deducable = null;
Set<PConstraint> snapshotConstraints = // avoid ConcurrentModificationX
new HashSet<PConstraint>(this.referringConstraints);
for (PConstraint constraint : snapshotConstraints) {
constraint.replaceVariable(this, replacement);
}
// replacementCheck() will fail from this point
this.unifiedInto = replacement;
pBody.noLongerUnique(this);
}
}
/**
* Determines whether there are any constraints that can deduce this variable
*/
public boolean isDeducable() {
replacementCheck();
if (deducable == null) {
deducable = false;
for (PConstraint pConstraint : getReferringConstraints()) {
if (pConstraint.getDeducedVariables().contains(this)) {
deducable = true;
break;
}
}
}
return deducable;
}
/**
* Register that this variable is referred by the given constraint.
*
* @param constraint
*/
public void refer(PConstraint constraint) {
pBody.checkMutability();
replacementCheck();
deducable = null;
referringConstraints.add(constraint);
}
/**
* Register that this variable is no longer referred by the given constraint.
*
* @param constraint
*/
public void unrefer(PConstraint constraint) {
pBody.checkMutability();
replacementCheck();
deducable = null;
referringConstraints.remove(constraint);
}
/**
* @return the name of the pattern variable. This is the unique key of the pattern node.
*/
public String getName() {
replacementCheck();
return name;
}
/**
* @return the virtual
*/
public boolean isVirtual() {
replacementCheck();
return virtual;
}
/**
* @return the referringConstraints
*/
public Set<PConstraint> getReferringConstraints() {
replacementCheck();
return referringConstraints;
}
@SuppressWarnings("unchecked")
public <ConstraintType> Set<ConstraintType> getReferringConstraintsOfType(Class<ConstraintType> constraintClass) {
replacementCheck();
Set<ConstraintType> result = new HashSet<ConstraintType>();
for (PConstraint pConstraint : referringConstraints) {
if (constraintClass.isInstance(pConstraint))
result.add((ConstraintType) pConstraint);
}
return result;
}
@Override
public String toString() {
// replacementCheck();
return name;// + ":PatternNode";
}
public PVariable getDirectUnifiedInto() {
return unifiedInto;
}
public PVariable getUnifiedIntoRoot() {
PVariable nextUnified = unifiedInto;
PVariable oldUnifiedInto = this;
while (nextUnified != null) {
oldUnifiedInto = nextUnified;
nextUnified = oldUnifiedInto.getDirectUnifiedInto();
}
return oldUnifiedInto; // unifiedInto;
}
public boolean isUnique() {
return unifiedInto == null;
}
private void replacementCheck() {
if (unifiedInto != null)
throw new IllegalStateException("Illegal usage of variable " + name + " which has been replaced with "
+ unifiedInto.name);
}
}
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