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retracts from the database the clauses which are unifiable with the argument.
retract(+Clause)
retract/1 retracts the first clause from the database which is unifiable with Clause .
If Clause is an atom or compound term whose principal functor is
different from ':-'/2 then Clause is the head and 'true' is the body
of the clause.
If Clause is a compound term whose principal functor is
':-'/2 then the left side (1st argument) of ':-' is the head
and the right side (2nd argument) the body
of the clause.
Arguments
Clause atom or compound term
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.
| retract(f(a)). | Succeeds. The database contains now the clauses:
colour(blue). colour(yellow) :- true. colour(blue,yellow) :- green. add(X,Y,Z) :- Z is X+Y. f(a) :- b. |
Standard
This predicate is part of the ISO-Prolog Standard.
See also
asserta/1, assertz/1, abolish/1, collect/3, load/1, unload/1, load/1/2, retractall/1.| document: http://www.ifcomputer.co.jp/MINERVA/Manual/Reference/Predicates/clause_creat_destruct/retract/print_en.html published 2008/10/6 update 2003/2/26 (c) 1996-2006 IF Computer Japan | ||||||||
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