Stopping halfway, not fun anymore, moving on

day14/main.hs

@@ -126,6 +126,72 @@ solvePart1 input = do
     fullMem = foldMap (runInitBlock I.empty) . reverse
 --
 
+-- Part 2 starts by redefining the meaning for the bits in the mask
+--
+data BM = BMUnchanged
+        | BMForceOne
+        | BMFloating
+
+instance Show (BM)
+  where
+    show BMUnchanged = "⁰"
+    show BMForceOne  = "¹"
+    show BMFloating  = "^"
+
+type Mask2 = [BM]
+
+data InitBlock2 = InitBlock2 { unMask2 :: Mask2, unInitLines2 :: [(Addr,Int)] }
+  deriving Show
+
+data Program2 = Program2 { unMem2 :: Mem, unInits2 :: [InitBlock2] }
+  deriving Show
+
+mkBM :: String -> Mask2
+mkBM xs | length xs == 36 = map go xs
+  where
+    go '1' = BMForceOne
+    go '0' = BMUnchanged
+    go 'X' = BMFloating
+    go c   = trace ("Illegal char: " <> show c) $ undefined
+mkBM xs | otherwise = trace "Mask is not 36 bit long" $ undefined
+
+
+-- We have to redo the parsing side, because we were too specific (gotcha!)
+--
+parseMask2 :: Parser Mask2
+parseMask2 = do
+  maskStr <- "mask = " *> P.take 36
+  P.endOfLine
+  pure $ mkBM $ T.unpack maskStr
+
+-- mem[x] = y
+parseInitLines2 :: Parser (Addr,Int)
+parseInitLines2 = do
+  x <- "mem[" *> P.decimal
+  y <- "] = " *> P.decimal
+  P.endOfLine
+  pure $ (x,y)
+
+parseBlock2 :: Parser InitBlock2
+parseBlock2 = do
+  mask <- parseMask2
+  ix <- P.many1 parseInitLines
+  pure $ InitBlock2 mask ix
+
+parseInput2 :: Parser [InitBlock2]
+parseInput2 = do
+  bx <- P.many1 parseBlock2
+  P.endOfInput
+  pure bx
+
+applyMask2 :: Mask2 -> Int -> [BM]
+applyMask2 xs a = map go (zip xs (showIntAtBase (2::Int) intToDigit a ""))
+  where
+    go (BMForceOne ,_   )  = BMForceOne
+    go (BMUnchanged,'1' )  = BMForceOne
+    go (BMUnchanged,'0' )  = BMUnchanged
+    go (BMFloating ,_   )  = BMFloating
+    go (nb,_) = trace "Invalid char in base 2 number" $ undefined
 
 main :: IO ()
 main = do
@@ -141,3 +207,7 @@ main = do
   putStrLn ":: Day 14 - Part 1"
   print . solvePart1 . T.pack $ exampleData
   print . solvePart1 $ input
+  putStrLn ":: Tests - Part 2"
+  print $ mkBM "000000000000000000000000000000X1001X"
+  print $ applyMask2 (mkBM "000000000000000000000000000000X1001X") (42::Int)
+  putStrLn ":: Day 14 - Part 2"