Reference zack's tryouts

scratch/git_visit.py

+# (* OCaml: non tail-recursive version *)
+
+# let rec visit obj =
+#   if not (is_in_cache obj) then begin
+#     List.iter visit (get_parents obj);
+#     store_object obj
+#   end
+
+# let _ = visit root_obj
+
+
+# (* OCaml: (almost) tail-recursive version *)
+
+# let visit obj =
+#   let rec aux visit_todo store_todo =
+#     match visit_todo with
+#     | [] -> store_todo
+#     | obj :: rest ->
+#        if not (is_in_cache obj) then
+# 	 let parents = get_parents obj in
+#          (* "@" is not tail-rec in OCaml (length of 1st arg.), but we don't
+#             care here, as equivalent operators might be tail-rec in other
+#             languages. To be tail-rec in OCaml we would need List.rev_append
+#             here, and to do reverse gymnastic elsewhere. *)
+# 	 aux (rest @ parents) (obj :: store_todo)
+#   in
+#   let objects_to_store = aux [obj] [] in
+#   List.iter store_object objects_to_store
+
+# let _ = visit root_obj
+
+from collections import deque
+
+def visit(root_obj, cache, store):
+
+    to_visit = deque([root_obj])  # FIFO
+    to_store = deque()            # LIFO
+
+    while to_visit:  # 1st pass: visit top-down, use cache, collect to_store
+        obj = to_visit.popleft()  # extract from beginning (left)
+        if obj not in cache:
+            to_visit.extend(obj.parents)  # append to end (right)
+            to_store.append(obj)
+
+    while to_store:  # 2nd pass: store objects bottom-up
+        obj = to_store.pop()
+        store.add(obj)