| 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.
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