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demonstrates that there's much more to cognition than logic.

=head2 Checking if a list is a subset of another list.

Usage:  C<subset(Subset, List).>

This definition depends on the C<member/2> predicate defined in this document.

 subset([Head|Tail], List) :-
    member(Head, List),
    subset(Tail, List).
 subset([], _). % The empty list is a subset of all lists

=head2 Delete all occurences of a term from a list, giving a new list.

Usage:  C<delete(Term, List, Result).>

 delete(_,[],[]). % deleting anything from an empty list yields an empty list
 delete(Term, [Term|Tail], Result) :- 
    delete(Term, Tail, Result).
 delete(Term, [Head|Tail], [Head|TailResult]) :- 
    delete(Term, Tail, TailResult).

=head2 Partition a list where list values <= Value.

Usage: C<partition(Value, List, LHS, RHS).>

Note that the term at I<Value> will be included in the I<LHS>.

 partition(Value, [Head|Tail], [Head|LHS], RHS) :-
    Head <= Value,
    partition(Value, Tail, LHS, RHS).
 partition(Value, [Head|Tail], LHS, [Head|RHS]) :-
    partition(Value, Tail, LHS, RHS).
 partition(_,[],[],[]).

=head2 Quicksort.

Usage: C<sort(List, Sorted).>

This definition depends on the C<partition/4> and C<append/3> predicates
defined in this document.

 sort([], []).
 sort([Head|Tail], Sorted) :-
    partition(Head, Tail, LHS, RHS),
    sort(LHS, Temp1),
    sort(RHS, Temp2),
    append(Temp1, [Head|Temp2], Sorted).

Note that (currently), this will only sort numeric values.

=head1 SEE ALSO

L<AI::Prolog>

L<AI::Prolog::Builtins>

L<AI::Prolog::Introduction>

W-Prolog:  L<http://goanna.cs.rmit.edu.au/~winikoff/wp/>

X-Prolog:  L<http://www.iro.umontreal.ca/~vaucher/XProlog/>

Roman BartE<225>k's online guide to programming Prolog:
L<http://kti.ms.mff.cuni.cz/~bartak/prolog/index.html>

=head1 AUTHOR

Curtis "Ovid" Poe, E<lt>moc tod oohay ta eop_divo_sitrucE<gt>

Reverse the name to email me.

=head1 COPYRIGHT AND LICENSE

Copyright 2005 by Curtis "Ovid" Poe

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself. 

=cut