Day 21, with major part a cleanups and improved comments.

src/AOC-21b.hs

@@ -14,7 +14,7 @@ splits = M.assocs $ roll 3 (M.singleton 0 1) where
   roll 0 m = m
   roll n m = roll (n-1) . M.unionsWith (+) . map ((`M.mapKeys` m) . (+)) $ [1,2,3]
 
--- universes (xScore,xPos,yScore,yPos) = (losers,winners)
+-- universes ! (xScore,xPos,yScore,yPos) = (losers,winners)
 -- where player X will make the next move.
 
 universes :: Array (Int,Int,Int,Int) (Integer,Integer)