day14/haskell: replace map-filter-enumerate with findIndices

day14/day14.hs

@@ -5,6 +5,7 @@ module Day14 where
 import AoC
 
 import Data.Bits
+import Data.List
 import Data.Map (Map)
 import qualified Data.Map as M
 import Data.Maybe
@@ -26,7 +27,7 @@ parseMaskDecl :: ReadP Mask
 parseMaskDecl = do
     string "mask = "
     mask <- many1 (choice $ char <$> "01X")
-    let extractMask c = foldl setBit zeroBits . map fst . filter ((==c) . snd) . enumerate 0 . reverse $ mask
+    let extractMask c = foldl setBit zeroBits . findIndices (==c) . reverse $ mask
     return $ Mask { set = extractMask '1'
                   , clear = extractMask '0'
                   , dontcare = extractMask 'X'