[Haskell-cafe] Re: Lazy Parsing
gue.schmidt at web.de
Sun May 31 07:45:15 EDT 2009
thank you very much for your help.
> I am curious to know what made you go wrong with the tutorial, and
> caused that you could not find the solution below?
Well let's first agree that I'm not very bright. I hate to admit it, but
it's a simple fact ;-).
Second let's agree that the uu-parsinglib is a *very* sophisticated
beast, I have not seen anything else like it out there, my sincere
congratulations for it. Thirdly the tutorial is also a very
sophisticated beast, and forthly, well just see point 1 :-).
And I just figured out why I was unable to write even that simple parser.
The code you sent me works just fine, I copied and pasted it, no problems.
But, as soon as I comment out the "main" function the type checker
complains, because now the ghci's type checker can no longer infer the
types of pDate or pDot. And this is exactly what happened. I kept
getting error messages from ghci, eventhough I had defined my parsers
possible correctly, but, *minus* the type signatures *and* minus any
main function that called it.
In hindsight I realize that this is a trap I have walked into many times
before, I guess I still have not acquired a Haskellers intuition.
I promise to do better next time :)
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