Package org.projog.core.predicate.builtin.compare

Class UnifyWithOccursCheck

java.lang.Object

org.projog.core.predicate.AbstractSingleResultPredicate

org.projog.core.predicate.builtin.compare.UnifyWithOccursCheck

All Implemented Interfaces:

KnowledgeBaseConsumer, PredicateFactory

public final class UnifyWithOccursCheck
extends AbstractSingleResultPredicate

unify_with_occurs_check(X, Y) - an equality test using sound unification.

Works like X = Y but with an additional check to avoid cyclic terms. When using unify_with_occurs_check a variable can only be unified with a term if that term does not contain the variable.

Constructor Summary

Constructors

Constructor	Description
UnifyWithOccursCheck()

Method Summary

Modifier and Type	Method	Description
protected boolean	evaluate(Term arg1, Term arg2)
private boolean	isCyclic(Term t)
private boolean	isCyclic(Term t, Set<Term> parents)

Methods inherited from class org.projog.core.predicate.AbstractSingleResultPredicate

evaluate, evaluate, evaluate, evaluate, evaluate, getArithmeticOperators, getFileHandles, getKnowledgeBase, getOperands, getPredicate, getPredicates, getProjogListeners, getSpyPoints, getTermFormatter, init, isRetryable, setKnowledgeBase

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.projog.core.predicate.PredicateFactory

isAlwaysCutOnBacktrack

Constructor Details

UnifyWithOccursCheck

public UnifyWithOccursCheck()

Method Details

evaluate

protected boolean evaluate(Term arg1,
 Term arg2)

Overrides:

evaluate in class AbstractSingleResultPredicate

isCyclic

private boolean isCyclic(Term t)

isCyclic

private boolean isCyclic(Term t,
 Set<Term> parents)