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

src/AOC-21b.hs

@@ -14,24 +14,24 @@ 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 ! (xCount,xPos,yCount,yPos) = (losers,winners)
 -- where player X will make the next move.
 
 universes :: Array (Int,Int,Int,Int) (Integer,Integer)
-universes = array bds [(p, score p) | p <- range bds] where
+universes = array bds [(p, counts p) | p <- range bds] where
   bds = ((0,1,0,1),(20,10,20,10))
-  score (xScore,xPos,yScore,yPos) = 
+  counts (xCount,xPos,yCount,yPos) = 
     sumPairs
       [ (c * losers, c * winners)
       | (r,c) <- splits
       , let nPos = ((xPos + r - 1) `mod` 10) + 1
-            nScore = xScore + nPos
-            (winners,losers) = univ yScore yPos nScore nPos
+            nScore = xCount + nPos
+            (winners,losers) = univ yCount yPos nScore nPos
       ]
   sumPairs = foldr1 (\(a,b) (c,d) -> (a+c,b+d))
-  univ xScore xPos yScore yPos
-    | yScore >= 21 = (1,0)
-    | otherwise = universes ! (xScore,xPos,yScore,yPos)
+  univ xCount xPos yCount yPos
+    | yCount >= 21 = (1,0)
+    | otherwise = universes ! (xCount,xPos,yCount,yPos)
   
 diracGame :: Int -> Int -> (Integer,Integer)
 diracGame p1 p2 = universes ! (0,p1,0,p2)