Clarify when crOldPos is set

src/Dodge/Creature/State.hs

@@ -57,9 +57,7 @@ stateUpdate f = foldCr
     , invSideEff
     , movementSideEff
     , f
-    , internalUpdate -- note that updateMovement needs to be evaluated at the correct moment
-                    -- wrt any changes in position made by the creature: the
-                    -- oldPos needs to be correctly set
+    , internalUpdate 
     , checkDeath
     ]
 
@@ -92,11 +90,6 @@ dropByState cr w = foldr (copyInvItemToFloor cr) w $ case cr ^. crState . crDrop
     DropSpecific xs -> xs
     DropAmount n -> take n $ evalState (shuffle $ IM.keys $ _crInv cr) (_randGen w)
 
-setOldPos :: Creature -> Creature
-setOldPos cr = cr
-    & crOldPos .~ _crPos cr
-    & crOldDir .~ _crDir cr
-
 doDamage :: Creature -> World -> World
 doDamage cr w = w
     & creatures . ix (_crID cr) . crState . crDamage .~ [] 
@@ -185,8 +178,8 @@ weaponReloadSounds cr w = case cr ^? crInv . ix (_crInvSel cr) . itConsumption o
 
 updateMovement :: Creature -> Creature
 updateMovement cr 
-    | isFrictionless cr = over crPos (+.+ momentum) $ setOldPos cr
-    | otherwise = updateWalkCycle $ setOldPos cr
+    | isFrictionless cr = over crPos (+.+ momentum) cr
+    | otherwise = updateWalkCycle cr
   where
     momentum' = 0.98 *.* (_crPos cr -.- _crOldPos cr)
     momentum'' | magV momentum' > 1 = 1 *.* normalizeV momentum'