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https://github.com/FiloSpaTeam/plutus-pioneer-program.git
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31 lines
1,016 B
Haskell
31 lines
1,016 B
Haskell
module Week04.Either where
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import Text.Read (readMaybe)
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import Week04.Monad
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readEither :: Read a => String -> Either String a
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readEither s = case readMaybe s of
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Nothing -> Left $ "can't parse: " ++ s
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Just a -> Right a
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foo :: String -> String -> String -> Either String Int
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foo x y z = case readEither x of
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Left err -> Left err
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Right k -> case readEither y of
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Left err -> Left err
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Right l -> case readEither z of
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Left err -> Left err
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Right m -> Right (k + l + m)
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bindEither :: Either String a -> (a -> Either String b) -> Either String b
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bindEither (Left err) _ = Left err
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bindEither (Right x) f = f x
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foo' :: String -> String -> String -> Either String Int
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foo' x y z = readEither x `bindEither` \k ->
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readEither y `bindEither` \l ->
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readEither z `bindEither` \m ->
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Right (k + l + m)
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foo'' :: String -> String -> String -> Either String Int
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foo'' x y z = threeInts (readEither x) (readEither y) (readEither z)
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