A* node: use dataclass (ruff)

Author: inducer

pytools/graph.py

@@ -118,6 +118,13 @@ def reverse_graph(graph: GraphT[NodeT]) -> GraphT[NodeT]:
 
 # {{{ a_star
 
+@dataclass(frozen=True)
+class _AStarNode(Generic[NodeT]):
+    state: NodeT
+    parent: _AStarNode[NodeT] | None
+    path_cost: float | int
+
+
 def a_star(
         initial_state: NodeT, goal_state: NodeT, neighbor_map: GraphT[NodeT],
         estimate_remaining_cost: Callable[[NodeT], float] | None = None,
@@ -135,19 +142,11 @@ def estimate_remaining_cost(x: NodeT) -> float:
                 return 1
             return 0
 
-    class AStarNode:
-        __slots__ = ["parent", "path_cost", "state"]
-
-        def __init__(self, state: NodeT, parent: Any, path_cost: float) -> None:
-            self.state = state
-            self.parent = parent
-            self.path_cost = path_cost
-
     inf = float("inf")
     init_remcost = estimate_remaining_cost(initial_state)
     assert init_remcost != inf
 
-    queue = [(init_remcost, AStarNode(initial_state, parent=None, path_cost=0))]
+    queue = [(init_remcost, _AStarNode(initial_state, parent=None, path_cost=0))]
     visited_states = set()
 
     while queue:
@@ -156,7 +155,7 @@ def __init__(self, state: NodeT, parent: Any, path_cost: float) -> None:
 
         if top.state == goal_state:
             result = []
-            it: AStarNode | None = top
+            it: _AStarNode[NodeT] | None = top
             while it is not None:
                 result.append(it.state)
                 it = it.parent
@@ -174,7 +173,7 @@ def __init__(self, state: NodeT, parent: Any, path_cost: float) -> None:
             estimated_path_cost = top.path_cost+step_cost+remaining_cost
             heappush(queue,
                 (estimated_path_cost,
-                    AStarNode(state, top, path_cost=top.path_cost + step_cost)))
+                    _AStarNode(state, top, path_cost=top.path_cost + step_cost)))
 
     raise RuntimeError("no solution")