4.12.5 Removing Clauses from the Database

• ref-mdb-rcd-efu: A Note on Efficient Use of retract/1

This section briefly describes the predicates used to remove the clauses and/or properties of a predicate from the system.

Please note: Removing all of a predicate's clauses by retract/1 and/or erase/1 (see ref-mdb-rcd-efu) does not remove the predicate's properties (and hence its definition) from the system. The only way to completely remove a predicate's clauses and properties is to use abolish/[1,2].

retract(:C)

erase the first dynamic clause that matches C

retractall(:H)

erase every clause whose head matches H

abolish(:F)

abolish the predicate(s) specified by F

abolish(:F,+O)

abolish the predicate(s) specified by F with options O

erase(+R)

erase the clause or recorded term (see ref-mdb-idb) with reference R