Commit 61899d4

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further cleaning of day 21

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Original file line number	Diff line number	Diff line change
`@@ -16,6 +16,8 @@ type Rule = M.Map Grid Grid`
`16`	`16`	`-- \| All 8 symmetries (elements of D8)`
`17`	`17`	`--`
`18`	`18`	`-- Generated by r, r^2, r^3, r^4, and flip times all of those`
	`19`	`+--`
	`20`	`+-- Thanks to https://en.wikipedia.org/wiki/Dihedral_group_of_order_8`
`19`	`21`	`symmetries :: Grid -> [Grid]`
`20`	`22`	`symmetries g = rots ++ (mirror <$> rots)`
`21`	`23`	`where`
`@@ -55,12 +57,11 @@ step r g = over (subgrids n) (r M.!) g`
`55`	`57`	\| length g `mod` 3 == 0 = 3
`56`	`58`	`\| otherwise = error "hello there"`
`57`	`59`
`58`		`-grid0 :: Grid`
`59`		`-grid0 = map (== '#') <$> [".#.","..#","###"]`
`60`		`-`
`61`	`60`	`day21 :: Int -> Rule -> Int`
`62`	`61`	`day21 n r = length . filter id . concat`
`63`	`62`	`$ iterate (step r) grid0 !!! n`
	`63`	`+ where`
	`64`	`+ grid0 = map (== '#') <$> [".#.","..#","###"]`
`64`	`65`
`65`	`66`	`day21a :: Challenge`
`66`	`67`	`day21a = show . day21 5 . parse`

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