Class Once

java.lang.Object

org.projog.core.predicate.AbstractSingleResultPredicate

org.projog.core.predicate.builtin.compound.Once

All Implemented Interfaces:

KnowledgeBaseConsumer, PredicateFactory, PreprocessablePredicateFactory

public final class Once
extends AbstractSingleResultPredicate
implements PreprocessablePredicateFactory

once(X) - calls the goal represented by a term.

The once(X) goal succeeds if an attempt to satisfy the goal represented by the term X succeeds. No attempt is made to retry the goal during backtracking - it is only evaluated once.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static final class	Once.OptimisedOnce

Constructor Summary

Constructors

Constructor	Description
Once()

Method Summary

Modifier and Type	Method	Description
protected boolean	evaluate(Term t)
PredicateFactory	preprocess(Term term)

Methods inherited from class AbstractSingleResultPredicate

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

Methods inherited from class Object

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

Methods inherited from interface PredicateFactory

getPredicate, isAlwaysCutOnBacktrack, isRetryable

Constructor Details

Once

public Once()

Method Details

evaluate

protected boolean evaluate(Term t)

Overrides:

evaluate in class AbstractSingleResultPredicate

preprocess

public PredicateFactory preprocess(Term term)

Specified by:

preprocess in interface PreprocessablePredicateFactory