PLOGHELP RETRACT                              Chris Mellish, August 1982
                                Revised by Kathryn Seifert  October 1986

Predicate to remove clauses matching a given pattern from database

    ?- retract(X).

Keywords: remove, database, retraction

Removes clause X from the database. If X matches several clauses, the
first will be removed. If the goal is resatisfied, subsequent matching
clauses will be removed, one by one. Each time, X will become
instantiated to the clause just removed.

-- RELATED DOCUMENTATION ----------------------------------------------

PLOGHELP * DATABASE
 Overview of Prolog database operations

PLOGHELP * RETRACTALL
 Predicate to remove clauses with a given head from database.

PLOGHELP * ABOLISH
 Predicate removing clauses with a given functor and arity from database