Fix thunk leak

src/Dodge/Update.hs

@@ -24,7 +24,7 @@ import Data.List
 import Data.Maybe
 import Data.Function
 import qualified Data.Set as S
-import qualified Data.IntMap.Lazy as IM
+import qualified Data.IntMap.Strict as IM
 import Control.Lens
 import Data.Monoid
 import System.Random
@@ -184,7 +184,9 @@ updateSeenWalls w = foldl' markWallSeen w wallsToUpdate
                              $ nRays 20
 
 markWallSeen :: World -> Wall -> World
-markWallSeen w wl = w & walls . ix (_wlID wl) . wlSeen .~ True
+markWallSeen w wl = w { _walls = IM.adjust mw (_wlID wl) $ _walls w }
+  where
+    mw wl' = wl' {_wlSeen = True}
 
 --setTestStringIO :: IO World -> IO World
 --setTestStringIO = fmap (\ w -> set testString (show $ s w) w)
@@ -310,6 +312,6 @@ visibleWalls p1 p2 ws
     . sortOn (dist p1 . fromJust . fst) 
     . filter ((/=) Nothing . fst) 
     . map f 
-    $ IM.toList ws
+    $ IM.elems ws
   where 
-    f (i,wl) = (uncurry intersectSegSeg (_wlLine wl) p1 p2, wl)
+    f wl = (uncurry intersectSegSeg (_wlLine wl) p1 p2, wl)