[enhance] Set: choose become quicker

It gave the minimum element in O(log(n))
Now it works in O(1), giving the element in the top of the tree

Conflicts:

	libbase/baseSetSig.ml
	libbase/intSet.ml

libbase/baseSet.ml

@@ -319,7 +319,9 @@ struct
   let add_list l t = List.fold_left (fun acc v -> add v acc) t l
   let from_list l = add_list l empty
 
-  let choose = min_elt
+  let choose = function
+    | Empty -> raise Not_found
+    | Node(_, v, _, _) -> v
 
   let rec choose_opt = function
     | Empty -> None

libbase/intSet.ml

@@ -69,7 +69,7 @@ let inter set set' = filter (fun x -> mem x set') set
 let diff set set' = filter (fun x -> not (mem x set')) set
 let subset (set:t) (set':t) = for_all (fun x -> mem x set') set
 
-let choose = min_elt
+let choose t = fst (IntMap.choose t)
 
 let choose_opt (set:t) =
   match IntMap.choose_opt set with