The data types I used are: data (Error e) => Reply e s a= Ok [s] a | Empty | Fail e data (Error e) => Result e s a = Accepted (Reply e s a) | Rejected newtype (Error e) => Parser e s a = Parser {runParser :: [s] -> Result e s a} newtype (Error e,Monad m) => ParserT e s m a = ParserT {runParserT :: [s] -> m (Result e s a)} data ParserError = UnspecifiedError | ErrorMsg String deriving Show instance Error ParserError where noMsg = UnspecifiedError strMsg s = ErrorMsg s Hope this makes things clearer... Regards, Keean Schupke Department of Electrical & Electronic Engineering, Imperial College London. Ken Shan wrote:
Can you please give your definition of the Parser and ParserT type constructors? My guesses are:
data State = ... data Message = ... data Accept a = Fail Message | Empty | Ok State a data Decide a = Rejected | Accepted a
data Parser a = Parser (State -> Decide (Accept a)) data ParserT m a = Parser (State -> m (Decide (Accept a)))
I wonder if it wouldn't be possible to redefine ParserT as
data ParserT m a = Parser (State -> m (Decide (m (Accept a))))
?
-- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig The trick is that there is no trick.
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