Add filtering on branches mid-iteration.

python_experiments/depth_first_search/depth_first_search.py

@@ -25,6 +25,7 @@ def main():
         activity_tree,
         lambda act: act.id in (2, 5, 10),
         lambda act: act.id in (4,),
+        lambda act: act.id in (1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
     )
 
     while (depth_and_node := match_iter.get_next()) is not None:
@@ -61,17 +62,20 @@ class MatchIter:
     stack: deque[StackEntry]
     is_match: Callable[[Activity], bool]
     is_transparent: Callable[[Activity], bool]
+    is_alive: Callable[[Activity], bool]
 
     def __init__(
         self,
         activity_tree: ActivityTree,
         is_match: Callable[[Activity], bool],
         is_transparent: Callable[[Activity], bool],
+        is_alive: Callable[[Activity], bool],
     ) -> None:
         self.activity_tree = activity_tree
         self.stack = deque([StackEntry(0)])
         self.is_match = is_match
         self.is_transparent = is_transparent
+        self.is_alive = is_alive
 
     def get_next(self) -> tuple[int, bool, bool, Activity] | None:
         if (next_announce := self.get_next_announce()) is not None:
@@ -104,7 +108,9 @@ class MatchIter:
             stack_entry.transparent = self.is_transparent(node)
 
             children = [
-                c for c in self.activity_tree.activities.values() if c.parent == node.id
+                c
+                for c in self.activity_tree.activities.values()
+                if c.parent == node.id and self.is_alive(c)
             ]
             # for c in children:
             for c in reversed(children):