[Haskell-cafe] parsec: parserFail & multiple error messages

[Albert Y. C. Lai]

On 12-08-08 03:24 PM, silly8888 wrote:
> The problem is that when I try this
>
> parse integer "" "70000"
>
> I get the following error:
>
> Left (line 1, column 6):
> unexpected end of input
> expecting digit
> integer overflow
>
> ie there are three error messages but I only want the last one. Is
> there something I can do about this?

import Text.Parsec
import Text.Parsec.String

integer :: Parser Int
integer = try integ3r <?> "number at most 65535"
integ3r  = do s <- many1 digit
               let n = read s
               if n > 65535 then
                   unexpected "number overflow"
               else
                   return n

main = do
   parseTest integer "a70000"
   parseTest integer "70000"