On Thu, Jun 21, 2007 at 03:34:54PM +0930, Levi Stephen wrote:
Is there a way through combining types/parsers that the double do block in primary could be avoided?
I understand it's necessary right now because the parsers identifier and stringLiteral return different types, so I can't just write:
i <- identifier <|> stringLiteral
You can use the fact that (GenParser tok st) is a monad and use liftM: i <- liftM PrimaryIdentifier identifier <|> liftM PrimaryLiteral stringLiteral I often find it convenient to use "choice" instead of <|> for long more complicated alternatives, for example like this: primary = choice [ do i <- identifier return $ PrimaryIdentifier i , do l <- stringLiteral return $ PrimaryLiteral l ]
So, I'm not sure whether my types need work,
I have a feeling that Identifier and Literal could just be type synonyms, because newtype's don't seem to be neccesary or beneficial here. I could be wrong though - after all, I don't know your intentions and the rest of the program. Best regards Tomek