Package org.projog.core.predicate.builtin.list

Class Length.Retryable

  • All Implemented Interfaces:
    Predicate
    Enclosing class:
    Length
    private static class Length.Retryable
extends java.lang.Object
implements Predicate

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private Retryable​(int startLength, Term list, Term length)  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean couldReevaluationSucceed()
      Could the next re-evaluation of this instance succeed?
      boolean evaluate()
      Attempts to satisfy the goal this instance represents.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • startLength

        final int startLength

      • list

        final Term list

      • length

        final Term length

      • currentLength

        int currentLength

    • Constructor Detail

      • Retryable

        private Retryable​(int startLength,
                  Term list,
                  Term length)

    • Method Detail

      • evaluate

        public boolean evaluate()
        Description copied from interface: Predicate
        Attempts to satisfy the goal this instance represents.

        Calling this method multiple times on a single instance allows all possible answers to be identified. An attempt to find a solution carries on from where the last successful call finished.

        If PredicateFactory.isRetryable() returns false then this method should only be called once per individual query (no attempt should be made to find alternative solutions).

        If PredicateFactory.isRetryable() returns true then, in order to find all possible solutions for an individual query, this method should be recalled on backtracking until it returns false.

        Specified by:
        evaluate in interface Predicate
        Returns:
        true if it was possible to satisfy the clause, false otherwise
        See Also:
        PredicateFactory.getPredicate(Term[])

      • couldReevaluationSucceed

        public boolean couldReevaluationSucceed()
        Description copied from interface: Predicate
        Could the next re-evaluation of this instance succeed?

        Specifies whether a specific instance of a specific implementation of Predicate, that has already had Predicate.evaluate() called on it at least once, could possibly return true the next time Predicate.evaluate() is called on it. i.e. is it worth trying to continue to find solutions for the specific query this particular instance represents and has been evaluating?

        (Note: the difference between this method and PredicateFactory.isRetryable() is that PredicateFactory.isRetryable() deals with whether, in general, a specific implementation (rather than instance) of Predicate could ever produce multiple answers for an individual query.)

        Specified by:
        couldReevaluationSucceed in interface Predicate
        Returns:
        true if an attempt to re-evaluate this instance could possible succeed, false otherwise