org.projog.core.predicate.builtin.list

Class Last

java.lang.Object

org.projog.core.predicate.AbstractPredicateFactory

org.projog.core.predicate.builtin.list.Last

All Implemented Interfaces:

KnowledgeBaseConsumer, PredicateFactory

public final class Last
extends AbstractPredicateFactory

last(X,Y) - finds the last element of a list.

Constructor Summary

Constructors

Constructor and Description
Last()

Method Summary

Modifier and Type	Method and Description
protected Predicate	getPredicate(Term list, Term termToUnifyLastElementWith)
boolean	isRetryable() Should instances of this implementation be re-evaluated when backtracking?

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

getArithmeticOperators, getFileHandles, getKnowledgeBase, getOperands, getPredicate, getPredicate, getPredicate, getPredicate, getPredicate, getPredicates, getProjogListeners, getSpyPoints, getTermFormatter, init, 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 Detail

Last

public Last()

Method Detail

getPredicate

protected Predicate getPredicate(Term list,
                                 Term termToUnifyLastElementWith)

Overrides:

getPredicate in class AbstractPredicateFactory

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

Overrides:

isRetryable in class AbstractPredicateFactory

Returns:

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