From ef8671a794fce06d62933b5ec825bc793a1d94d9 Mon Sep 17 00:00:00 2001
From: Xiretza <xiretza@xiretza.xyz>
Date: Fri, 4 Dec 2020 10:34:46 +0100
Subject: [PATCH] 2020 day3/haskell: make it more readable

---
 2020/day3/day3.hs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/2020/day3/day3.hs b/2020/day3/day3.hs
index 5d9cb30..53dfa13 100644
--- a/2020/day3/day3.hs
+++ b/2020/day3/day3.hs
@@ -11,7 +11,13 @@ f .: g = (f .) . g
 infixl 8 .:
 
 countHits :: (Int, Int) -> [[Bool]] -> Int
-countHits = length . filter id . map (uncurry $ flip (!!)) . catMaybes .: compose2 (zipWith mzip) (uncurry . flip $ compose2 intercalate (flip replicate empty . pred) (fmap pure . map pure . enumFromThen 0)) (map pure)
+countHits = length . filterMap lookup . catMaybes .: compose2 (zipWith mzip) maybeIndices justLines
+    where justRightSteps = map (pure . Just) . enumFromThen 0
+          downNothings = flip replicate Nothing . pred
+          maybeIndices = uncurry $ compose2 (flip intercalate) justRightSteps downNothings
+          justLines = map Just
+          lookup = uncurry $ flip (!!)
+          filterMap = filter id .: map
 
 treeCharToBool :: Char -> Bool
 treeCharToBool = (== '#')