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day16/haskell: prettify findSingletonChoice

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Xiretza 2020-12-16 17:49:01 +01:00
parent 477f518531
commit 6dee5caf29
1 changed files with 6 additions and 5 deletions
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11
2020/day16/day16.hs
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@ -66,11 +66,12 @@ resolve = sequence . map fromResolved . iterateUntilNothing resolve' . map (Choi
fromResolved _ = Nothing
findSingletonChoice :: [Resolve a] -> Maybe (a, [Resolve a])
findSingletonChoice (c@(Choice s):xs) | S.size s == 1 = let [x] = S.elems s
in Just (x, Resolved x:xs)
| otherwise = (fmap.fmap) (c:) $ findSingletonChoice xs
findSingletonChoice (x:xs) = (fmap.fmap) (x:) $ findSingletonChoice xs
findSingletonChoice _ = Nothing
findSingletonChoice [] = Nothing
findSingletonChoice (x:xs) =
case x of
Choice s | S.size s == 1 -> let [r] = S.elems s
in Just (r, Resolved r : xs)
_ -> fmap (\(r, rest) -> (r, x:rest)) $ findSingletonChoice xs
resolve' :: Ord a => [Resolve a] -> Maybe [Resolve a]
resolve' xs = do