From bf1c37113721e522c2d4fd18bc94abe2d024e957 Mon Sep 17 00:00:00 2001
From: Quinten Kock <quintenkock@gmail.com>
Date: Mon, 20 Dec 2021 14:03:35 +0100
Subject: [PATCH] split out some map stuff

---
 2021/day20.hs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/2021/day20.hs b/2021/day20.hs
index ccf8cf7..ce849dd 100644
--- a/2021/day20.hs
+++ b/2021/day20.hs
@@ -30,7 +30,8 @@ next :: Algorithm -> Image -> Image
 next algo (Img def diff) = Img (newDefault algo def) newDiff where
     nonDefault = foldr (\(x,y) -> insertManyWith (++) (neighs x y)) M.empty diff
     neighs x y = map (\i -> ((x-1 + i `mod` 3, y-1 + i `div` 3), [i])) [0..8]
-    calcNonDef = M.filter (/= newDefault algo def) $ M.map (\ns -> algo A.! binToDec (nonDefToNum ns)) nonDefault
+    known = M.map (\ns -> algo A.! binToDec (nonDefToNum ns)) nonDefault
+    calcNonDef = M.filter (/= newDefault algo def) known
     nonDefToNum ns = map (\i -> if i `elem` ns then not def else def) [0..8]
     newDiff = M.keys calcNonDef