* http://cs.unibo.it/helm/.
*)
-(*
- * implementazione del comando INTERSECT
- *)
-(*
- * eccezione sollevata quando il join dei contesti
- * deve essere vuoto
- *)
-exception Join_must_be_empty;;
+(* Catenates two lists preserving order and getting rid of duplicates *)
+let rec append (l1,l2) =
+ match l1,l2 with
+ [],_ -> l2
+ | _,[] -> l1
+ | s1::tl1, s2::_ when s1 < s2 -> s1::append (tl1,l2)
+ | s1::_, s2::tl2 when s2 < s1 -> s2::append (l1,tl2)
+ | s1::tl1, s2::tl2 -> s1::append (tl1,tl2)
-(*
- * join fra due contesti
- *)
-let xres_join_context h1 l1 h2 l2 =
- match (l1, l2) with
- ([], _) -> l2
- | (_, []) -> l1
- | (_, _) ->
- let hh = h2 @ (List.find_all (function t -> not (List.mem t h2)) h1)
- and m1 = List.combine h1 l1
- and m2 = List.combine h2 l2
- in
- List.map
- (fun elem ->
- let value1 = try (List.assoc elem m1) with Not_found -> List.assoc elem m2
- and value2 = try (List.assoc elem m2) with Not_found -> List.assoc elem m1
- in
- if value1 = value2 then value1 else raise Join_must_be_empty
- )
- hh
;;
-(*
- *
- *)
-let intersect_tails h1 t1 h2 t2 =
- let rec aux t1 t2 =
- match (t1, t2) with
- ([], _)
- | (_, []) -> []
- | ((l1::tl1)::tll1, (l2::tl2)::tll2) ->
- if l1 = l2 then
- try
- (*match xres_join_context h1 tl1 h2 tl2 with
- [] -> aux tll1 tll2
- | t -> (l1::(xres_join_context h1 tl1 h2 tl2))::(aux tll1 tll2)*)
- (l1::(tl1 @ tl2))::(aux tll1 tll2)
- with
- Join_must_be_empty -> aux tll1 tll2
- else
- if l1 < l2 then
- aux tll1 t2
- else
- aux t1 tll2
- | _ -> assert false
- in
- aux t1 t2
+
+(* Sums two attribute groups preserving order *)
+let rec sum_groups(gr1, gr2) =
+ match gr1, gr2 with
+ [],_ -> gr2
+ | _,[] -> gr1
+ | gr1, gr2 when gr1 = gr2 -> gr1
+ | (key1,l1)::tl1, (key2,l2)::_ when key1 < key2 -> (key1,l1)::(sum_groups (tl1,gr2))
+ | (key1,l1)::_, (key2,l2)::tl2 when key2 < key1 -> (key2,l2)::(sum_groups (gr1,tl2))
+ | (key1,l1)::tl1, (key2,l2)::tl2 -> (key1,(append (l1,l2)))::(sum_groups (tl1,tl2))
+
;;
-(*
- * implementazione del comando INTERSECT
- *)
-let intersect_ex l1 l2 =
- let _ = print_string ("INTERSECT ")
- and t = Unix.time () in
- let result =
- match (l1, l2) with
- ((head1::tail1), (head2::tail2)) ->
- (match (head1, head2) with
- ([], _) -> assert false (* gli header non devono mai essere vuoti *)
- | (_, []) -> assert false (* devono contenere almeno [retVal] *)
- | (_, _) ->
- (match (tail1, tail2) with
- ([], _) -> [["retVal"]] (* se una delle due code e' vuota... *)
- | (_, []) -> [["retVal"]] (* ... l'intersezione e' vuota *)
- | (_, _) ->
- [head2 @
- (List.find_all
- (function t -> not (List.mem t head2))
- head1
- )
- ] (* header del risultato finale *)
- @
- intersect_tails (List.tl head1) tail1 (List.tl head2) tail2
- (*
- List.fold_left
- (fun par1 elem1 -> par1 @
- List.map
- (fun elem2 ->
- [(List.hd elem1)] @
- (xres_join_context (List.tl head1) (List.tl elem1)
- (List.tl head2) (List.tl elem2)
- )
- )
- (List.find_all (* *)
- (fun elem2 -> (* trova tutti gli elementi della lista tail2 *)
- ((List.hd elem1) = (List.hd elem2)) && (* che stanno in tail1 *)
- not ((xres_join_context (List.tl head1) (List.tl elem1)
- (List.tl head2) (List.tl elem2)) = [])
- (* e per i quali la xres_join_context non sia vuota *)
- )
- tail2 (* List.find_all *)
- )
- )
- []
- tail1 (* per ogni elemento di tail1 applica la List.fold_left *)
- *)
- ) (* match *)
- )
- | _ -> []
- in
- let _ = print_endline (string_of_float (Unix.time () -. t)); flush stdout in
- result
+(* Product between an attribute set and a group of attributes *)
+let rec sub_prod (aset, gr) = (*prende un aset e un gr, fa la somma tra tutti i gruppi di aset e gr*)
+ match aset with
+ [] -> []
+ | gr1::tl1 -> sum_groups (gr1, gr)::(sub_prod(tl1, gr))
+;;
+
+
+(* Cartesian product between two attribute sets*)
+let rec prod (as1, as2) =
+ match as1, as2 with
+ [],_ -> []
+ | _,[] -> []
+ | gr1::tl1, _ -> append((sub_prod (as2, gr1)), (prod (tl1, as2))) (* chiamo la sub_prod con un el. as1 e as2 *)
;;
+(* Intersection between two resource sets, preserves order and gets rid of duplicates *)
+let rec intersect_ex rs1 rs2 =
+ match (rs1, rs2) with
+ [],_
+ | _,[] -> []
+ | (uri1,_)::tl1, (uri2,_)::_ when uri1 < uri2 -> intersect_ex tl1 rs2
+ | (uri1,_)::_, (uri2,_)::tl2 when uri2 < uri1 -> intersect_ex rs1 tl2
+ | (uri1,as1)::tl1, (uri2,as2)::tl2 -> (uri1, prod(as1,as2))::intersect_ex tl1 tl2
+;;