Hi Gerd, despite SourcePos being abstract, it can be fully manipulated using newPos. import Text.ParserCombinators.Parsec.Pos If you can compute the positions from your Tok-stream then you may consider using "tokenPrim" and work with "GenParser Tok () a" HTH Christian Gerd M wrote:
I'm trying to use parsec for parsing a custom input stream. As far as I understood the manual correctly I need to define the primitive parser:
type MyParser a = GenParser (SourcePos,Tok) () a mytoken :: (Tok -> Maybe a) -> MyParser a mytoken test = token showToken posToken testToken where showToken (pos,tok) = show tok posToken (pos,tok) = pos testToken (pos,tok) = test tok
The problem is, since SourcePos is an abstract datatype, how can I actually run this parser without explicitly using values of type SourcePos in the input stream?