[r2004-12-23 00:33:43 by afrisch] comments

Original author: afrisch
Date: 2004-12-23 00:33:43+00:00

types/patterns.ml

@@ -1658,6 +1658,28 @@ x=(1,2)
       | TConj of Types.t * fv * ('a,'b) t * ('a,'b) t
       | TOther of descr * Types.t * fv * 'b
 
+    let capt pr p = 
+      if IdMap.is_empty pr then p else match p with
+	| TCapt (pr2,p) -> TCapt (TargExpr.merge pr pr2,p)
+	| TFail -> TFail
+	| p ->  TCapt (pr,p)
+
+    let rec conj a1 fv1 r1 r2 = match (r1,r2) with
+      | TSucceed,r | r,TSucceed -> r
+      | TFail,r | r,TFail -> TFail
+      | TCapt (f,r1), r2 | r2, TCapt (f,r1) -> capt f (conj a1 fv1 r1 r2)
+      | r1,r2 -> TConj (a1,fv1,r1,r2)
+
+    let alt p a1 r1 r2 = match (r1,r2) with
+      | TFail,r | r,TFail -> r
+      | TSucceed, _ -> assert false
+	  (* Note: this cannot happen because if the lhs succeeds,
+	     then the rhs must fail (it is evaluated under
+	     the assumption that the lhs fails, so the static
+	     assumption is empty in this case). *)
+      | r1,r2 -> TAlt (p,a1,r1,r2)
+
+
     let get_result = function
       | TCapt (r,TSucceed) -> Some r
       | TFail -> None
@@ -1692,23 +1714,6 @@ x=(1,2)
 	| Record (l,q) -> oth (`Record (l,q))
 	| Dummy -> assert false
 
-    let capt pr p = 
-      if IdMap.is_empty pr then p else match p with
-	| TCapt (pr2,p) -> TCapt (TargExpr.merge pr pr2,p)
-	| TFail -> TFail
-	| p ->  TCapt (pr,p)
-
-    let rec conj a1 fv1 r1 r2 = match (r1,r2) with
-      | TSucceed,r | r,TSucceed -> r
-      | TFail,r | r,TFail -> TFail
-      | TCapt (f,r1), r2 | r2, TCapt (f,r1) -> capt f (conj a1 fv1 r1 r2)
-      | r1,r2 -> TConj (a1,fv1,r1,r2)
-
-    let alt p a1 r1 r2 = match (r1,r2) with
-      | TFail,r | r,TFail -> r
-      | r1,r2 -> TAlt (p,a1,r1,r2)
-
-
     let factorize ((a,_,_) as p) t xs f =
       if Types.disjoint a t then TFail
       else
@@ -1730,6 +1735,10 @@ x=(1,2)
 	    (fun xs ->
 	       alt p a1 (optimize t xs p1) (optimize (Types.diff t a1) xs p2))
       | TConj (a1,fv1,p1,p2) ->
+	  (* We don't factorize above a & pattern eagerly, because
+	     if factorization would occur, it would also
+	     occur below and be lifted by the conj function, which
+	     produces the same effect. *)
 	  conj a1 fv1
 	    (optimize t (IdSet.cap xs fv1) p1)
 	    (optimize (Types.cap t a1) (IdSet.diff xs fv1) p2)