On Wed, Aug 8, 2012 at 8:26 PM, silly8888 <silly8...@gmail.com> wrote: > Inserting a character into the stream can be expensive if for example > the stream is a ByteString. > I tried the following crazy solution and it seems that it works: > > succeed :: Parser () > succeed = mkPT $ \st -> > return $ Consumed $ return $ Ok () st $ unknownError st > > succeed is a parser that always succeeds without really consuming any > input but it also resets the error state. >
Because you're using the 'Consumed' constructor, you're also telling parsec not the back-track if there any errors following this parsers. This means that 'succeed >> failingParser' won't backtrack, even if 'failingParser' doesn't consume input. Are you using your original parser within a larger parser? Are the error messages also not great? Antoine _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
