Merge pull request #39 from ephemient/hs/day4

hs/src/Day4.hs

@@ -5,20 +5,20 @@
 -- Description:    <https://adventofcode.com/2024/day/4 Day 4: Ceres Search>
 module Day4 (part1, part2) where
 
-import Control.Monad (ap, guard)
-import Data.Function (on)
+import Control.Monad (guard)
 import Data.List (tails)
 import Data.Text (Text)
 import Data.Text qualified as T (drop, lines, reverse, splitAt, transpose, unpack, zip)
 import Data.Text.Internal.Search qualified as T (indices)
 
 part1 :: Text -> Int
-part1 input = sum $ ((+) `on` length . T.indices "XMAS") `ap` T.reverse <$> grid ++ T.transpose grid ++ concat diagonals
+part1 input = sum $ countXmas <$> grid ++ T.transpose grid ++ concat diagonals
   where
     grid = T.lines input
     diagonals = do
       (lower, upper) <- unzip . zipWith T.splitAt [0 ..] <$> [grid, reverse grid]
       T.transpose <$> [T.reverse <$> lower, upper]
+    countXmas line = length (T.indices "XMAS" line) + length (T.indices "SAMX" line)
 
 part2 :: Text -> Int
 part2 input = length $ do