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mvaldesdeleon/needs-more-operators.hs

Last active August 12, 2018 20:04
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needs-more-operators.hs
asInt :: String -> Either String Int
asInt ('-':xs) = negate <$> asInt xs
asInt xs =
foldl
(\acc x -> acc >>= addNextDigit x)
(Right 0)
xs
where addNextDigit x acc = if isDigit x
then Right $ acc * 10 + digitToInt x
else Left $ "non-digit"
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