Dynamic predicates

Version: 1.5#118 (2000/4/19, 18:13:43 CEST)

Version of last change: 0.5#30 (1998/6/30, 14:23:37 MET DST)

This module implements the assert/retract family of predicates to manipulate dynamic predicates.

The predicates defined in this module allow modification of the program as it is actually running. Clauses can be added to the program (asserted) or removed from the program (retracted). For these predicates, the argument which corresponds to the clause head must be instantiated to an atom or a compound term. The argument corresponding to the clause must be instantiated either to a term Head :- Body or, if the body part is empty, to Head. An empty body part is represented as true.

• Usage and interface (dynamic)
• Documentation on exports (dynamic)
• Documentation on multifiles (dynamic)

Usage and interface (dynamic)

Documentation on exports (dynamic)

PREDICATE: asserta/1:

Meta-predicate with arguments: asserta(clause).

Usage: asserta(+Clause)

• Description: The current instance of Clause is interpreted as a clause and is added to the current program. The predicate concerned must be dynamic. The new clause becomes the first clause for the predicate concerned. Any uninstantiated variables in the Clause will be replaced by new private variables.
• The following properties should hold globally: Documentation is still incomplete: asserta(+Clause) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: asserta/2:

Meta-predicate with arguments: asserta(clause,?).

Usage: asserta(+Clause,-(Ref))

• Description: Like asserta/1. Ref is a unique identifier of the asserted clause.
• The following properties should hold globally: Documentation is still incomplete: asserta(+Clause,-(Ref)) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: assertz/1:

Meta-predicate with arguments: assertz(clause).

Usage: assertz(+Clause)

• Description: Like asserta/1, except that the new clause becomes the last clause for the predicate concerned.
• The following properties should hold globally: Documentation is still incomplete: assertz(+Clause) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: assertz/2:

Meta-predicate with arguments: assertz(clause,?).

Usage: assertz(+Clause,-(Ref))

• Description: Like assertz/1. Ref is a unique identifier of the asserted clause.
• The following properties should hold globally: Documentation is still incomplete: assertz(+Clause,-(Ref)) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: assert/1:

Meta-predicate with arguments: assert(clause).

Usage: assert(+Clause)

• Description: Identical to assertz/1. Included for compatibility.
• The following properties should hold globally: Documentation is still incomplete: assert(+Clause) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: assert/2:

Meta-predicate with arguments: assert(clause,?).

Usage: assert(+Clause,-(Ref))

• Description: Identical to assertz/2. Included for compatibility.
• The following properties should hold globally: Documentation is still incomplete: assert(+Clause,-(Ref)) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: retract/1:

Meta-predicate with arguments: retract(clause).

Usage: retract(+Clause)

• Description: The first clause in the program that matches Clause is erased. The predicate concerned must be dynamic. The predicate retract/1 may be used in a non-determinate fashion, i.e., it will successively retract clauses matching the argument through backtracking. If reactivated by backtracking, invocations of the predicate whose clauses are being retracted will proceed unaffected by the retracts. This is also true for invocations of clause for the same predicate. The space occupied by a retracted clause will be recovered when instances of the clause are no longer in use.
• The following properties should hold globally: Documentation is still incomplete: retract(+Clause) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: retractall/1:

Meta-predicate with arguments: retractall(fact).

Usage: retractall(+Head)

• Description: Erase all clauses whose head matches Head, where Head must be instantiated to an atom or a compound term. The predicate concerned must be dynamic. The predicate definition is retained.
• The following properties should hold globally: Documentation is still incomplete: retractall(+Head) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: abolish/1:

Meta-predicate with arguments: abolish(spec).

Usage: abolish(+Spec)

• Description: Erase all clauses of the predicate specified by the predicate spec, or list of predicate specs, Spec. The predicate definition itself is also erased (the predicate is deemed undefined after execution of the abolish). The predicates concerned must all be user defined.
• The following properties should hold globally: Documentation is still incomplete: abolish(+Spec) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: clause/2:

Meta-predicate with arguments: clause(fact,?).

Usage: clause(+Head,?(Body))

• Description: The clause 'Head :- Body' exists in the current program. The predicate concerned must be dynamic.
• The following properties should hold globally: Documentation is still incomplete: clause(+Head,?(Body)) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: clause/3:

clause(Head,Body,Ref)

Like clause(Head,Body), plus the clause is uniquely identified by Ref.

Meta-predicate with arguments: clause(fact,?,?).

Usage 1: clause(+Head,?(Body),?(Ref))

• Description: Head must be instantiated to an atom or a compound term.
• The following properties should hold globally: Documentation is still incomplete: clause(+Head,?(Body),?(Ref)) may not conform the functionality documented. (doc_props:doc_incomplete/1)

Usage 2: clause(?(Head),?(Body),+Ref)

• Description: Ref must be instantiated to a valid identifier.
• The following properties should hold globally: Documentation is still incomplete: clause(?(Head),?(Body),+Ref) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: current_predicate/1:

Usage: current_predicate(?(Spec))

• Description: A user defined predicate is named Spec.
• The following properties should hold globally: Documentation is still incomplete: current_predicate(?(Spec)) may not conform the functionality documented. (doc_props:doc_incomplete/1)

PREDICATE: dynamic/1:

No further documentation available for this predicate.

PREDICATE: data/1:

No further documentation available for this predicate.

PREDICATE: wellformed_body/3:

wellformed_body(BodyIn,Env,BodyOut)

BodyIn is a well-formed clause body. BodyOut is its counterpart with no single-variable meta-goals (i.e., with call(X) for X). Env denotes if global cuts are admissible in BodyIn (+ if they are, - if they are not).

Documentation on multifiles (dynamic)

PREDICATE: do_on_abolish/1:

do_on_abolish(Head)

A hook predicate which will be called when the definition of the predicate of Head is abolished.

The predicate is multifile.

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