On Sun, Jul 13, 2025 at 01:34:15PM +0200, Stefan Klinger wrote:
I've been bugged by the silent overflowing of integer parsers as provided by `base`, `attoparsec`, and others. I'd go so far as to call it a bug when the user types `298` and the parser says `Right 42`.
Fortunately, silent overflow when parsing bounded integers is not a behaviour of either the ByteString or streaming-bytestring libraries. $ ghci -v0 λ> import Data.ByteString.Char8 λ> :t readInt8 readInt8 :: ByteString -> Maybe (GHC.Internal.Int.Int8, ByteString) λ> readInt8 $ pack "42 foo" Just (42," foo") λ> readInt8 $ pack "342 foo" Nothing λ> readInt16 $ pack "342 foo" Just (342," foo") λ> readInt16 $ pack "76342 foo" Nothing λ> readInt32 $ pack "76342 foo" Just (76342," foo") λ> readInt32 $ pack "9876531042 foo" Nothing λ> readInt64 $ pack "9876531042 foo" Just (9876531042," foo") The bytestring library also supports the various Word sizes, Integer and Natural! Similarly, (be it for just the Int type): [viktor@chardros m]$ cabal repl -z -v0 --build-depend streaming-bytestring λ> import Streaming.ByteString.Char8 λ> import Data.Functor.Of λ> import Data.Functor.Compose λ> import Data.Bifoldable λ> (x :> _) <- getCompose <$> readInt (string "42 foo") λ> print x Just 42 λ> (x :> _) <- getCompose <$> readInt (string "9876543210987654210 foo") λ> print x Nothing
Unfortunately, all parsing libraries I've looked at get this wrong. A [solution][4] is proposed below.
There were more libraries to look at. -- Viktor.