+
+
+let rec compare_query_tree q1 q2 =
+ q1.id==q2.id|| match q1.desc,q2.desc with
+ | Binop(op1,qt1,qt2),Binop(op2,qt3,qt4)->op1==op2&& ((compare_query_tree qt1 qt3 && compare_query_tree qt2 qt4)
+ || (compare_query_tree qt1 qt4 && compare_query_tree qt2 qt3))
+ | Axis(a1,qt1),Axis(a2,qt2) -> compare_axis a1 a2 && compare_query_tree qt1 qt2
+ | Tag(t1,k1),Tag(t2,k2) ->t1==t2&& k1==k2
+ | Dom,Dom | Start,Start ->true
+ | _,_ ->false
+
+and compare_axis a1 a2 =
+ match a1,a2 with
+ Self ,Self | Attribute, Attribute | Child , Child | Parent , Parent
+ | FollowingSibling , FollowingSibling
+ | PrecedingSibling , PrecedingSibling
+ | Preceding , Preceding | Following , Following -> true
+ | Descendant b1, Descendant b2 -> b1==b2
+ | Ancestor b1, Ancestor b2 -> b1==b2
+ | _,_ -> false
+
+let mini_id = ref 0
+let mini_table = QTreeHash.create 17
+
+let rec minimize_qtree q =
+ if q.id != -1 then q
+ else
+ try
+ QTreeHash.find mini_table q
+ with Not_found ->
+ let mdesc =
+ match q.desc with
+ (Start | Dom | Tag _) as d -> d
+ | Binop(op,q1,q2) -> let mq1 = minimize_qtree q1 in
+ let mq2 = minimize_qtree q2 in
+ Binop(op,mq1,mq2)
+ | Axis(a,q1) -> let mq1 = minimize_qtree q1 in
+ Axis(a,mq1)
+ in
+ q.desc <- mdesc;
+ q.hash <- QTree.hash q;
+ q.id <- !mini_id;
+ incr mini_id;
+ QTreeHash.add mini_table q q;
+ q
+
+
+
+let rec eval_qtree tree start q =