readIntP :: Num a => a -> (Char -> Bool) -> (Char -> Int) -> ReadP a
Dunno, but one could guess that people find this function more convenient to apply, in the spirit of readIntP x (('0' <=) .&&. (<= '9')) ((- ord '0') . ord) One could always add your function, under a different name. They easily convert into each other, using a function like boolToMaybe :: Bool -> a -> Maybe a boolToMaybe True a = Just a boolToMaybe False _ = Nothing On 2020-06-06 01:04, Dannyu NDos wrote:
Current type signature of readIntP is:
readIntP :: Num a => a -> (Char -> Bool) -> (Char -> Int) -> ReadP a
This seems kinda redundant. It inputs two functions, one checking whether a character is valid digit, and the other assigning an integer to the digit.
Shouldn't we merge them together to one function? Like this:
importControl.Monad importData.Foldable importData.Maybe importText.ParserCombinators.ReadP
readIntP:: Numa=> a-> (Char-> MaybeInt) -> ReadPa readIntP base valDigit = do maybeNs <- manyTill (fmap (fmap fromIntegral . valDigit) get) $ do str <- fmap (fmap valDigit) look casestr of []-> return () (Nothing:_) -> return () _ -> pfail letn = foldl' (\l r -> casel of Nothing -> r Just l1 -> fmap (base * l1 +) r ) Nothing maybeNs guard (isJust n) return (fromJust n)
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