Initial revision

[helm.git] / helm / ocaml / mathql_interpreter / intersect.ml

diff --git a/helm/ocaml/mathql_interpreter/intersect.ml b/helm/ocaml/mathql_interpreter/intersect.ml
index bd582a3b2ae8c1dbb9e6d56ede86ca1bea274a56..73bebaa507c2300f5bd90dcc4c5001d887744eae 100644 (file)
--- a/helm/ocaml/mathql_interpreter/intersect.ml
+++ b/helm/ocaml/mathql_interpreter/intersect.ml
@@ -23,85 +23,53 @@
  * 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
-      try 
-       (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
-       ) with
-        Join_must_be_empty -> []
 ;;
 
-(*
- * implementazione del comando INTERSECT
- *)
-let intersect_ex alist1 alist2 =
- let head1 = List.hd alist1
- and tail1 = List.tl alist1
- and head2 = List.hd alist2
- and tail2 = List.tl alist2 (* e fin qui ... *)
- in
-  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 *)
-          @
-          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
-             )
-             )
-           []
-           tail1 (* per ogni elemento di tail1 applica la List.fold_left *)
-      ) (* match *)
+
+(* 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))
+
 ;;
 
+(* 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 
+;;