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yap-6.3/ICLP2014_examples.yap

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2014-02-10 15:35:37 +00:00
:- initialization(yap_flag(tabling_mode, load_answers)).
% Required to activate rational term support within the table space.
/*
ICLP2014 submission - instack/2
*/
instack(E, [H|T]) :- E == H.
instack(E, [_H|T]) :- instack(E, T).
/*
ICLP2014 submission - Example 1. member_1/2
Cyclic safe predicate with the use of instack/2 predicate.
*/
member_1(E, L) :-
member(E, L, []).
member(E, [E|_T], _).
member(_E, L, S) :-
instack(L, S),
!,
fail.
member(E, [H|T], S) :-
member(E, T, [[H|T]|S]).
/*
ICLP2014 submission - Example 2. member_2/2
Cyclic safe predicate with the use of tabling.
*/
:- table member_2/2.
member_2(E, [E|_T]).
member_2(E, [_H|T]) :-
member_2(E, T).
/*
ICLP2014 submission - Example 3. bin/1
*/
:- table bin/1.
:- tabling_mode(bin/1, coinductive).
% The two above directives are the equivalent of the :- coinductive bin/1 directive
bin([0|T]) :- bin(T).
bin([1|T]) :- bin(T).
/*
ICLP2014 submission - Example 4. comember/2
*/
:- table comember/2.
:- tabling_mode(comember/2, coinductive).
% The two above directives are the equivalent of the :- coinductive comember/2 directive
comember(H, L) :-
drop(H, L, L1),
comember(H, L1).
:- table(drop/3).
drop(H, [H|T], T).
drop(H, [_|T], T1) :- drop(H, T, T1).
%%%%%%%%%%
/*
ICLP2014 submission - Example 5. alternative drop_2/3 definition.
This definition uses instack instead of tabling.
*/
drop_2(E, L, NL) :-
drop(E, L, NL, []).
drop(_E, L, _NL, S) :-
instack(L, S),
!,
fail.
drop(E, [E|T], T, _).
drop(E, [H|T], T1, S) :-
drop(E, T, T1, [[H|T]|S]).
/*
ICLP2014 submission - Example 6. canonical_term/2
The following predicate takes a rational term and returns
the same rational term in canonical form.
*/
canonical_term(Term, Canonical) :-
Term =.. InList,
decompose_cyclic_term(Term, InList, OutList, OpenEnd, [Term]),
Canonical =.. OutList,
Canonical = OpenEnd.
decompose_cyclic_term(_CyclicTerm, [], [], _OpenEnd, _Stack).
decompose_cyclic_term(CyclicTerm, [Term|Tail], [Term|NewTail], OpenEnd, Stack) :-
acyclic_term(Term), !,
decompose_cyclic_term(CyclicTerm, Tail, NewTail, OpenEnd, Stack).
decompose_cyclic_term(CyclicTerm, [Term|Tail], [OpenEnd|NewTail], OpenEnd, Stack) :-
CyclicTerm == Term, !,
decompose_cyclic_term(CyclicTerm, Tail, NewTail, OpenEnd, Stack).
decompose_cyclic_term(CyclicTerm, [Term|Tail], [Canonical|NewTail], OpenEnd, Stack) :-
\+ instack(Term, Stack), !,
Term =.. InList,
decompose_cyclic_term(Term, InList, OutList, OpenEnd2, [Term|Stack]),
Canonical =.. OutList,
( Canonical = OpenEnd2,
Canonical == Term,
!
; OpenEnd2 = OpenEnd
),
decompose_cyclic_term(CyclicTerm, Tail, NewTail, OpenEnd, Stack).
decompose_cyclic_term(CyclicTerm, [_Term|Tail], [OpenEnd|NewTail], OpenEnd, Stack) :-
decompose_cyclic_term(CyclicTerm, Tail, NewTail, OpenEnd, Stack).