org.projog.core.predicate

Class AbstractSingleResultPredicate

java.lang.Object

org.projog.core.predicate.AbstractSingleResultPredicate

All Implemented Interfaces:

KnowledgeBaseConsumer, PredicateFactory

Direct Known Subclasses:

AddArithmeticOperator, AddExpressionFactory, AddPredicateFactory, AddUserDefinedArithmeticOperator, AlterSpyPoint, AppendListOfLists, Arg, Assert, AtomicListConcat, Close, Compare, Consult, ConsultList, ConvertTime, CopyTerm, CurrentInput, CurrentOutput, Debugging, Delete, Dif, Distinct, Dynamic, EnsureLoaded, Equal, Erase, ExtremumList, Fail, FindAll, Flag, Flatten, Functor, GetChar, GetCode, GetTime, In, InsertRecord, Is, IsAtom, IsAtomic, IsCompound, IsFloat, IsInteger, IsList, IsNonVar, IsNumber, IsVar, KeySort, Listing, MemberCheck, NewLine, NoDebug, Not, NoTrace, NotStrictEquality, NotUnifiable, NumberVars, NumericConstraintPredicate, NumericEquality, NumericGreaterThan, NumericGreaterThanOrEqual, NumericInequality, NumericLessThan, NumericLessThanOrEqual, Once, Op, Open, PairsElements, PredSort, PutChar, Read, RetractAll, See, Seen, SetInput, SetOutput, Sort, SortAsSet, StrictEquality, SubList, Subset, SubtractFromList, Tab, Tell, TermGreaterThan, TermGreaterThanOrEqual, TermLessThan, TermLessThanOrEqual, TermSplit, Throw, Told, Trace, True, UnifyWithOccursCheck, Univ, Write, WriteCanonical, Writef

public abstract class AbstractSingleResultPredicate
extends Object
implements PredicateFactory, KnowledgeBaseConsumer

Superclass of "plug-in" predicates that are not re-evaluated as part of backtracking.

Provides a skeletal implementation of PredicateFactory and Predicate. No attempt to find multiple solutions will be made as part of backtracking as isRetryable() always returns false.

Constructor Summary

Constructors

Constructor and Description
AbstractSingleResultPredicate()

Method Summary

Modifier and Type	Method and Description
protected boolean	evaluate()
protected boolean	evaluate(Term arg)
boolean	evaluate(Term[] args)
protected boolean	evaluate(Term arg1, Term arg2)
protected boolean	evaluate(Term arg1, Term arg2, Term arg3)
protected boolean	evaluate(Term arg1, Term arg2, Term arg3, Term arg4)
protected ArithmeticOperators	getArithmeticOperators()
protected FileHandles	getFileHandles()
protected KnowledgeBase	getKnowledgeBase()
protected Operands	getOperands()
Predicate	getPredicate(Term[] args) Returns a Predicate to be used in the evaluation of a goal.
protected Predicates	getPredicates()
protected ProjogListeners	getProjogListeners()
protected SpyPoints	getSpyPoints()
protected TermFormatter	getTermFormatter()
protected void	init() This method is called by setKnowledgeBase(KnowledgeBase).
boolean	isRetryable() Should instances of this implementation be re-evaluated when backtracking?
void	setKnowledgeBase(KnowledgeBase knowledgeBase) Provides a reference to a KnowledgeBase.

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

AbstractSingleResultPredicate

public AbstractSingleResultPredicate()

Method Detail

getPredicate

public final 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()

evaluate

public final boolean evaluate(Term[] args)

evaluate

protected boolean evaluate()

evaluate

protected boolean evaluate(Term arg)

evaluate

protected boolean evaluate(Term arg1,
                           Term arg2)

evaluate

protected boolean evaluate(Term arg1,
                           Term arg2,
                           Term arg3)

evaluate

protected boolean evaluate(Term arg1,
                           Term arg2,
                           Term arg3,
                           Term arg4)

isRetryable

public final 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

setKnowledgeBase

public final void setKnowledgeBase(KnowledgeBase knowledgeBase)

Description copied from interface: KnowledgeBaseConsumer

Provides a reference to a KnowledgeBase.

Specified by:

setKnowledgeBase in interface KnowledgeBaseConsumer

init

protected void init()

This method is called by setKnowledgeBase(KnowledgeBase).

Can be overridden by subclasses to perform initialisation before any calls to evaluate(Term...) are made. As setKnowledgeBase(KnowledgeBase) will have already been called before this method is invoked, overridden versions will be able to access the KnowledgeBase using getKnowledgeBase().

getKnowledgeBase

protected final KnowledgeBase getKnowledgeBase()

getPredicates

protected final Predicates getPredicates()

getArithmeticOperators

protected final ArithmeticOperators getArithmeticOperators()

getProjogListeners

protected final ProjogListeners getProjogListeners()

getOperands

protected final Operands getOperands()

getTermFormatter

protected final TermFormatter getTermFormatter()

getSpyPoints

protected final SpyPoints getSpyPoints()

getFileHandles

protected final FileHandles getFileHandles()