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deletes from the database all clauses which head is unifiable with the argument.
retractall(+Head)
retractall/1 deletes all clauses from the database which
head is unifiable with Head.
That means that retractall/1 can be defined as:
retractall(Head) :- retract((Head :- _)), fail.
retractall(_).
Arguments
Head head of a clause
Examples
Assume that the database contains the clauses:
colour(blue).
colour(yellow).
colour(blue,yellow,green).
add(X,Y,Z) :- Z is X+Y.
f(a).
f(a) :- b.
| retractall(colour(X)). | Succeeds. The database contains now the clauses:
colour(blue,yellow,green). add(X,Y,Z) :- Z is X+Y. f(a). f(b) :- b. |
Standard
This predicate is not part of the ISO-Prolog Standard.
See also
asserta/1, assertz/1, abolish/1, collect/3, load/1, unload/1, load/1/2, retract/1.| document: http://www.ifcomputer.co.jp/MINERVA/Manual/Reference/Predicates/clause_creat_destruct/retractall/print_en.html published 2008/9/1 update 2003/2/26 (c) 1996-2006 IF Computer Japan | ||||||||
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