[Haskell-cafe] Re: Parsec Question

Gerd M gerd_m1977 at hotmail.com
Mon Jan 9 15:50:44 EST 2006

>despite SourcePos being abstract, it can be fully manipulated using newPos.
Thanks for the tip, I thought it wasn't exported.

>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?

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