Section "database"

Besides input/output, the dynamic database of a Prolog system provides further means to have side effects by Prolog code. Currently we do compile the surface of Prolog dynamic clauses to correctly handle the cut. Since this is still done in 100% Prolog it incures a little extra cost in storage and retrieval, when the clause has a body.

Otherwise clause store and retrieval is now mostly native code, which makes the dynamic database quite speedy for facts. The recent releases have also seen just-in-time indexing and assertion sharing, besides the program sharing that was already present in initial versions of Dogelog Player. The latest addition are pre-computed hash indexes.

The following database predicates are provided:

dynamic(I): [ISO 7.4.2.1]

The predicate succeeds. As a side effect, it touches the predicate I and ensures that it is dynamic.

prehash(I):

The predicate succeeds. As a side effect, it touches the predicate I and ensures that it is uses a pre-computed hash index.

asserta(C): [ISO 8.9.1]

The predicate succeeds. As a side effect, the clause C is inserted at the top.

assertz(C): [ISO 8.9.2]

The predicate succeeds. As a side effect, the clause C is inserted at the bottom.

clause(H, B): [ISO 8.8.1]

The predicate succeeds with the clauses that unify H :- B.

retract(C): [ISO 8.9.3]

The predicate succeeds with the clauses that unify C. As a side effect, the clause is removed.

retractall(H): [TC2 8.9.5]

The predicate succeeds. As a side effect, the clauses that unify the head H are removed.

abolish(I): [ISO 8.9.4]

The predicate succeeds. As a side effect, the predicate I is destroyed.

current_predicate(I): [ISO 8.8.2]

The predicate succeeds in I with current predicate indicators.

predicate_property(I, P):

The predicate succeeds in P with the properties of the predicate indicator I. The following properties are supported:

static: The predicate is static.

dynamic: The predicate is dynamic.

built_in: The predicate is built-in.

sys_multifile(S): The predicate is marked multifile in the source path S.

sys_usage(S): The predicate is defined in the source path S.

sys_discontiguous(S): The predicate is marked discontinuous in the source path S.

Use Privacy (c) 2005-2026 XLOG Technologies AG