Package org.projog.core.predicate.udp

Class InterpretedTailRecursivePredicateFactory

java.lang.Object

org.projog.core.predicate.udp.InterpretedTailRecursivePredicateFactory

All Implemented Interfaces:

PredicateFactory

public final class InterpretedTailRecursivePredicateFactory
extends java.lang.Object
implements PredicateFactory

Creates "tail recursion optimised" versions of user defined predicates.

Each instance of InterpretedTailRecursivePredicateFactory creates new instances of InterpretedTailRecursivePredicate for a specific user defined predicate. The user defined predicate must be judged as eligible for tail recursion optimisation using the criteria used by TailRecursivePredicateMetaData.

See Also:

TailRecursivePredicate, TailRecursivePredicateMetaData

Field Summary

Fields

Modifier and Type	Field	Description
private Term[]	firstClauseConsequentArgs
private Term[]	firstClauseOriginalTerms
private PredicateFactory[]	firstClausePredicateFactories
private TailRecursivePredicateMetaData	metaData
private Term[]	secondClauseConsequentArgs
private Term[]	secondClauseOriginalTerms
private PredicateFactory[]	secondClausePredicateFactories
private SpyPoints.SpyPoint	spyPoint

Constructor Summary

Constructors

Constructor	Description
InterpretedTailRecursivePredicateFactory(KnowledgeBase kb, TailRecursivePredicateMetaData metaData)

Method Summary

Modifier and Type	Method	Description
InterpretedTailRecursivePredicate	getPredicate(Term[] args)	Returns a Predicate to be used in the evaluation of a goal.
private static SpyPoints.SpyPoint	getSpyPoint(KnowledgeBase kb, TailRecursivePredicateMetaData metaData)
boolean	isRetryable()	Should instances of this implementation be re-evaluated when backtracking?
private boolean	isRetryable(Term[] args)

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

Field Detail

spyPoint

private final SpyPoints.SpyPoint spyPoint

metaData

private final TailRecursivePredicateMetaData metaData

firstClausePredicateFactories

private final PredicateFactory[] firstClausePredicateFactories

firstClauseConsequentArgs

private final Term[] firstClauseConsequentArgs

firstClauseOriginalTerms

private final Term[] firstClauseOriginalTerms

secondClausePredicateFactories

private final PredicateFactory[] secondClausePredicateFactories

secondClauseConsequentArgs

private final Term[] secondClauseConsequentArgs

secondClauseOriginalTerms

private final Term[] secondClauseOriginalTerms

Constructor Detail

InterpretedTailRecursivePredicateFactory

public InterpretedTailRecursivePredicateFactory(KnowledgeBase kb,
                                                TailRecursivePredicateMetaData metaData)

Method Detail

getPredicate

public InterpretedTailRecursivePredicate getPredicate(Term[] args)

Description copied from interface: PredicateFactory

Returns a Predicate to be used in the evaluation of a goal.

Specified by:

getPredicate in interface PredicateFactory

Parameters:

args - the arguments to use in the evaluation of the goal

Returns:

Predicate to be used in the evaluation of the goal

See Also:

Predicate.evaluate()

isRetryable

private boolean isRetryable(Term[] args)

getSpyPoint

private static SpyPoints.SpyPoint getSpyPoint(KnowledgeBase kb,
                                              TailRecursivePredicateMetaData metaData)

isRetryable

public boolean isRetryable()

Description copied from interface: PredicateFactory

Should instances of this implementation be re-evaluated when backtracking?

Some goals (e.g. X is 1) are only meant to be evaluated once (the statement is either true or false) while others (e.g. repeat(3)) are meant to be evaluated multiple times. For instances of Predicate that are designed to possibly have Predicate.evaluate() called on them multiple times for the same individual query this method should return true. For instances of Predicate that are designed to only be evaluated once per individual query this method should return false.

Specified by:

isRetryable in interface PredicateFactory

Returns:

true if an attempt should be made to re-evaluate instances of implementing classes when backtracking, false otherwise