4.12.8 The Internal Database

The following predicates are provided solely for compatibility with other Prolog systems. Their semantics can be understood by imagining that they are defined by the following clauses:

recorda(Key, Term, Ref) :- 
     functor(Key, Name, Arity),
     functor(F, Name, Arity),
     asserta('$recorded'(F,Term), Ref).
recordz(Key, Term, Ref) :-
     functor(Key, Name, Arity),
     functor(F, Name, Arity),
     assertz('$recorded'(F,Term), Ref).
recorded(Key, Term, Ref) :- 
     functor(Key, Name, Arity),
     functor(F, Name, Arity),
     clause('$recorded'(F,Term), _, Ref).

The reason for the calls to functor/3 in the above definition is that only the principal functor of the key is significant. If Key is a compound term, then its arguments are ignored.

Please note: Equivalent functionality and performance, with reduced memory costs, can usually be had through normal dynamic procedures and indexing (see ref-mdb-bas and Indexing).

recorda(Key, Term, Ref) records the Term in the internal database as the first item for the key Key; a database reference to the newly-recorded term is returned in Ref.

recordz(Key, Term, Ref) is like recorda/3 except that it records the term as the last item in the internal database.

recorded(Key, Term, Ref) searches the internal database for a term recorded under the key Key that unifies with Term, and whose database reference unifies with Ref.

current_key(KeyName, KeyTerm) succeeds when KeyName is the atom or integer that is the name of KeyTerm. KeyTerm is an integer, atom, or compound term that is the key for a currently recorded term.