On Wed, 11 Jun 2003 09:03:32 +0100
"Simon Peyton-Jones"
Check out "Embedding Prolog in Haskell", which explores exactly the topic you discuss.
http://citeseer.nj.nec.com/272378.html
Simon
and what can be considered a followup to that paper, http://citeseer.nj.nec.com/claessen00typed.html -- solve (do (x,y) <- free; append x y (s2l "abc"); -- liftM2 (,) (list atom x) (list atom y)) ==> -- ([],["a","b","c"]),(["a"],["b","c"]),(["a","b"],["c"]),(["a","b","c"],[ ]) append :: (Unify s a, Free s a) => List s a -> List s a -> List s a -> LP s () append ps qs rs = (do ps =:= Nil qs =:= rs) `mplus` (do (x,xs,ys) <- free ps =:= (x ::: xs) rs =:= (x ::: ys) append xs qs ys) -- append([],L,L). -- append([H|T],L,[H|Rest]) :- append(T,L,Rest). powerset' xs ys = free >>= \(h,t,rest) -> p2h [ [xs =:= Nil, ys =:= Nil], [xs =:= (h ::: t), powerset' t ys], [xs =:= (h ::: t), ys =:= (h ::: rest), powerset' t rest]] -- powerset([],[]). -- powerset([X|Xs],Rest) :- powerset(Xs,Rest) -- powerset([X|Xs],[X|Rest]) :- powerset(Xs,Rest).