After Union and Relation

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

diff --git a/helm/ocaml/mathql_interpreter/union.ml b/helm/ocaml/mathql_interpreter/union.ml
index c8e46cd0b8ee991c8f324c6b99b4464f67514d0f..a02fbd0f5f417a054a9dbf07961f3ab3b828763f 100644 (file)
--- a/helm/ocaml/mathql_interpreter/union.ml
+++ b/helm/ocaml/mathql_interpreter/union.ml
@@ -106,24 +106,25 @@ let union_ex alist1 alist2 =
        )
 ;;
 *)
+(* Merges two attribute group lists preserves order and gets rid of duplicates*)
+let rec merge l1 l2 =
+  match (l1,l2) with
+     [],l
+   | l,[] -> l
+   | g1::tl1,g2::_ when g1 < g2 -> g1::(merge tl1 l2)
+   | g1::_,g2::tl2 when g2 < g1 -> g2::(merge l1 tl2)
+   | g1::tl1,g2::tl2 -> g1::(merge tl1 tl2)
+;;       
 
 (* preserves order and gets rid of duplicates *)
-let rec union_ex l1 l2 =
- let module S = Mathql_semantics in
-  match (l1, l2) with
+let rec union_ex rs1 rs2 =
+  match (rs1, rs2) with
      [],l
    | l,[] -> l
-   | ({S.uri = uri1} as entry1)::tl1,
-     ({S.uri = uri2} as entry2)::_ when uri1 < uri2 ->
-       entry1::(union_ex tl1 l2)
-   | ({S.uri = uri1} as entry1)::_,
-     ({S.uri = uri2} as entry2)::tl2 when uri2 < uri1 ->
-       entry2::(union_ex l1 tl2)
-   | entry1::tl1,entry2::tl2 -> (* same entry *)
-      if entry1 = entry2 then (* same attributes *)
-       entry1::(union_ex tl1 tl2)
-      else
-       assert false
+   | (uri1,l1)::tl1,(uri2,_)::_ when uri1 < uri2 -> (uri1,l1)::(union_ex tl1 rs2)
+   | (uri1,_)::_,(uri2,l2)::tl2 when uri2 < uri1 -> (uri2,l2)::(union_ex rs1 tl2)
+   | (uri1,l1)::tl1,(uri2,l2)::tl2 -> if l1 = l2 then (uri1,l1)::(union_ex tl1 tl2)
+                                     else (uri1,merge l1 l2)::(union_ex tl1 tl2)       
 ;;
 
 let union_ex l1 l2 =