The predicates described in this section were introduced in early implementations of Prolog to provide efficient means of performing operations on large quantities of data. The introduction of indexed dynamic predicates have rendered these predicates obsolete, and the sole purpose of providing them is to support existing code. There is no reason whatsoever to use them in new code.
These predicates store arbitrary terms in the database without interfering with the clauses which make up the program. The terms which are stored in this way can subsequently be retrieved via the key on which they were stored. Many terms may be stored on the same key, and they can be individually accessed by pattern matching. Alternatively, access can be achieved via a special identifier which uniquely identifies each recorded term and which is returned when the term is stored.
recorded(?Key,?Term,?Ref) [Obsolescent]The internal database is searched for terms recorded under the key
Key. These terms are successively unified with Term in the
order they occur in the database. At the same time, Ref is
unified with the database reference to the recorded item. If the
key is instantiated to a compound term, only its principal functor is
significant. If the key is uninstantiated, all terms in the database
are successively unified with Term in the order they occur.
recorda(+Key,?Term,-Ref) [Obsolescent]The term Term is recorded in the internal database as the first
item for the key Key, where Ref is its
database reference. The key must be given, and only its
principal functor is significant. Any uninstantiated variables in the
Term will be replaced by new private variables, along with copies
of any subgoals blocked on these variables (see Procedural).
recordz(+Key,?Term,-Ref) [Obsolescent]Like recorda/3, except that the new term becomes the last
item for the key Key.
current_key(?KeyName,?KeyTerm) [Obsolescent]KeyTerm is the most general form of the key for a currently recorded term, and KeyName is the name of that key. This predicate can be used to enumerate in undefined order all keys for currently recorded terms through backtracking.