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 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

Constructor Summary

Constructors

Constructor and Description
InterpretedTailRecursivePredicateFactory(KnowledgeBase kb, TailRecursivePredicateMetaData metaData)

Method Summary

Modifier and Type	Method and Description
org.projog.core.predicate.udp.InterpretedTailRecursivePredicate	getPredicate(Term[] args) Returns a Predicate to be used in the evaluation of a goal.
boolean	isRetryable() Should instances of this implementation be re-evaluated when backtracking?

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 Detail

InterpretedTailRecursivePredicateFactory

public InterpretedTailRecursivePredicateFactory(KnowledgeBase kb,
                                                TailRecursivePredicateMetaData metaData)

Method Detail

getPredicate

public org.projog.core.predicate.udp.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

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