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20 lines
656 B
Idris
20 lines
656 B
Idris
import Data.List
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import Data.String
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byLength : Nat -> String -> Maybe (String, Nat)
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byLength n str = (str, n) <$ guard (String.length str == n)
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bySuccess : a -> (a -> Maybe b) -> Maybe b
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bySuccess = flip ($)
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-- cheating to display the remaining (const Nothing) function in 3rd case
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Show b => Show (List a -> b) where
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show f = "\\ _ => " ++ show (f [])
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main : IO ()
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main = putStr $ unlines
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[ show $ prefixOfBy byLength [5,5,1] ["hello", "world", "!", "Not", "seen"]
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, show $ suffixOfBy byLength [3,4] ["hello", "world", "!", "Not", "seen"]
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, show $ prefixOfBy bySuccess [[1],[1,2],[]] [head', head' <=< tail', const (pure 3), const Nothing]
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]
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