> returning an offset past the end of the string I feel if you're dealing with offsets into strings, it's probably easier to stop doing that rather than try to

> returning an offset past the end of the string I feel if you're dealing with offsets into strings, it's probably easier to stop doing that rather than try to get the type checker to prove it 'correct'. I tried a linear types implementation: newtype Parser a = P (String ⊸ (String, Maybe a)) parseChar :: Char -> Parser Char parseChar c = P $ \s -> case s of [] -> ([], Nothing) (x:xs) -> if x == c then (xs, Just c) else (xs, Nothing) This guarantees that the 's' is used exactly once instead of dropped on the floor. It's not great because I wanted to drop it on the floor. Here's it not compiling when I use the wrong string: ... then ("some string", Just c) ... • Couldn't match type ‘'Many’ with ‘'One’ arising from multiplicity of ‘s’ • In the second argument of ‘($)’, namely ‘\ s -> case s of