retract
Entity: predicate

retract_in
Entity: predicate

retractall
Entity: predicate

Usage:
retract(Clause)

Retracts the first clause which is unifiable with Clause .

Clause | the clause to retract.

Fails if there is no clause which is unifiable with Clause .

Usage:
retract_in(Clause)

Retracts the first clause which is unifiable with Clause both in the run-time database (like retract) and in the text file containing the running program.

Clause | the clause to retract. |

Fails if there is no clause which is unifiable with Clause.

Usage:
retractall(Clause)

Retracts all clauses which are unifiable with Clause .

Clause | the clause to retract.

Succeeds always.

Example:

?-retract_in(test(X)), write(X), nl, !, test(Y), write(Y), nl, fail.

test(1).
test(2).
test(3).

Run this example four times (press four times F5 ).

See also:

assert
assert_in