Package org.projog.core.predicate.udp

Class NeverSucceedsPredicateFactory

java.lang.Object

org.projog.core.predicate.udp.NeverSucceedsPredicateFactory

All Implemented Interfaces:

PredicateFactory

final class NeverSucceedsPredicateFactory
extends java.lang.Object
implements PredicateFactory

Field Summary

Fields

Modifier and Type	Field	Description
private SpyPoints.SpyPoint	spyPoint

Constructor Summary

Constructors

Constructor	Description
NeverSucceedsPredicateFactory(SpyPoints.SpyPoint spyPoint)

Method Summary

Modifier and Type	Method	Description
Predicate	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

Field Detail

spyPoint

private final SpyPoints.SpyPoint spyPoint

Constructor Detail

NeverSucceedsPredicateFactory

NeverSucceedsPredicateFactory(SpyPoints.SpyPoint spyPoint)

Method Detail

getPredicate

public Predicate 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