alice.tuprolog

Interface ClauseStore

All Known Implementing Classes:

CollectionItemsStore, DefaultClauseStore, HyperGraphClauseStore, MapEntriesStore

public interface ClauseStore

A list of clauses belonging to the same family as a goal. A family is composed by clauses with the same functor and arity. The clause store acts as an iterator where each call to the fetch method produces the next clause compatible with the current goal. The current goal and a list of local variables are normally passed to the ClauseStore implementation during constructions time (see the ClauseStoreFactory interface).

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Clause the store and free any external resources or caches associated with it.
ClauseInfo	fetch() Get the next clause compatible with the current goal.
boolean	hasCompatibleClause() Return true if there are more clauses compatible with the current goal, irrespective of local variable bindings.
boolean	haveAlternatives() Return true if there are more clauses available compatible with the current goal and false otherwise.

Method Detail

fetch

ClauseInfo fetch()

Get the next clause compatible with the current goal. As a side-effect, all variables local to the clause store should be freed and available for unification again.

haveAlternatives

boolean haveAlternatives()

Return true if there are more clauses available compatible with the current goal and false otherwise. A first call to this method is equivalent to a call to hasCompatibleClause (since no variables would have been bound as yet).

hasCompatibleClause

boolean hasCompatibleClause()

Return true if there are more clauses compatible with the current goal, irrespective of local variable bindings.

close

void close()

Clause the store and free any external resources or caches associated with it. This method must be implemented by variants that access external resources such disk or DBMSs.

This being a cleanup method, implementations should try not to throw any exceptions here. It should also be possible to call this method repeatedly on the same instance without failure.