Implementation of creature update using endofunctor monoid

src/Dodge/Update.hs

@@ -26,9 +26,11 @@ import Data.List
 import Data.Maybe
 import Data.Function
 import qualified Data.Set as S
-import qualified Data.IntMap.Strict as IM
+import qualified Data.IntMap.Lazy as IM
 import qualified Data.Map as M
 import Control.Lens
+import Data.Monoid
+import System.Random
 
 update :: World -> World
 update = update' . pushSideEffects
@@ -129,12 +131,21 @@ updateParticles w = set particles (catMaybes ps) w'
   where 
     (w',ps) = mapAccumR (\a b -> _ptUpdate' b a b) w $ _particles w
 
-updateCreatures :: World -> World
-updateCreatures w = f $ set randGen newG $ set creatures (IM.mapMaybe id crs) w
+updateCreatures' :: World -> World
+updateCreatures' w = f $ set randGen newG $ set creatures (IM.mapMaybe id crs) w
   where 
     ((f,newG),crs) = 
         IM.mapAccum (\g' cr -> _crUpdate cr w g' cr) (id,_randGen w) $ _creatures w
 
+updateToTM :: (World -> (World -> World,StdGen) -> Creature -> ((World -> World,StdGen), Maybe Creature)) -> World -> Creature -> (Endo World,  Maybe Creature)
+updateToTM u w cr = case u w (id,_randGen w) cr of
+    ((f,_),mcr) -> (Endo f,mcr)
+
+updateCreatures :: World -> World
+updateCreatures w = appEndo f $ creatures .~ IM.mapMaybe id m $ w
+  where
+    (f,m) = traverse (\cr -> updateToTM (_crUpdate cr) w cr) (_creatures w)
+
 {- |
 Apply door mechanisms.  -}
 updateWalls :: World -> World