HELP FLUSH                                              Aaron Sloman  Sept 1979

This procedure takes one argument, a pattern, and removes all items in the
database which it matches. Thus, it could be defined something like this:

    define flush(pattern);
        while present(pattern) do
            remove(it)
        endwhile
    enddefine;

Unlike REMOVE, FLUSH does not cause a mishap if it doesn't find a matching
item in the database.  If differs further from REMOVE in that it deletes ALL
matching database entries. E.g.

    [] -> database;
    add([i like fish]);
    add([i like fruit]);
    database =>
    ** [[i like fruit] [i like fish]])
    flush([i like ==]);
    database =>
    ** []

See also HELP * ADD, *PRESENT, *LOOKUP, *REMOVE, *DATABASE.