From 56a8dd2b30e462c28d15bae26551b42c2100d4e6 Mon Sep 17 00:00:00 2001
From: hi <hi>
Date: Tue, 12 Aug 2025 13:28:23 +0000
Subject: [PATCH] bfs: use a Set for visited nodes

---
 Logic/Graph.hs     | 8 +++++---
 Logic/Statement.hs | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/Logic/Graph.hs b/Logic/Graph.hs
index 0aa3be4..ba899ae 100644
--- a/Logic/Graph.hs
+++ b/Logic/Graph.hs
@@ -1,7 +1,9 @@
 module Logic.Graph where
 
-bfs :: Eq a => a -> a -> (a -> [(edge, a)]) -> Maybe [edge]
-bfs goal start getEdges = reverse <$> aux [([], start)] []
+import Data.Set (Set, insert)
+
+bfs :: (Eq a, Ord a) => a -> a -> (a -> [(edge, a)]) -> Maybe [edge]
+bfs goal start getEdges = reverse <$> aux [([], start)] mempty
   where
     aux [] _ = Nothing
     aux ((path, vertex):queue) visited
@@ -12,7 +14,7 @@ bfs goal start getEdges = reverse <$> aux [([], start)] []
           case filter (\(_, v) -> v == goal) new of
             [] ->
               let queue' = queue ++ map (\(edge, next) -> (edge:path, next)) new
-              in aux queue' (vertex:visited)
+              in aux queue' $ insert vertex visited
             ((edge, _):_) -> Just (edge:path)
 
     getUnvisitedAdjacent vertex visited =
diff --git a/Logic/Statement.hs b/Logic/Statement.hs
index f85fe26..6d7268b 100644
--- a/Logic/Statement.hs
+++ b/Logic/Statement.hs
@@ -9,7 +9,7 @@ data Statement
   | Or Statement Statement
   | Implies Statement Statement
   | Iff Statement Statement
-  deriving (Show, Eq)
+  deriving (Eq, Ord, Show)
 
 atoms :: Statement -> [String]
 atoms = toAscList . mkSet