Tomasz Zielonka
On Tue, Dec 18, 2007 at 05:38:47PM +0000, Jon Fairbairn wrote:
... or, "whoops! I've writtten another html combinator library."
History: I was surprised to find that all the Haskell html generating stuff I've tried allowed one to construct invalid HTML.
Did you take a look at Peter Thiemann's WASH/HTML?
I did.
It contains a monadic combinator library that checks proper nesting of HTML tags at compile time. The library also has an unchecked version,
It's possible that I only tried the unchecked version: I just thought of an invalid example, read what documentation I could find and generated some invalid html. However, Thiemann's thesis says The current library implements neither inclusions nor exceptions. So I hope I might be forgiven if I overlooked a difference between the distribution and the thesis! Does the checked version now enforce appendix B and prevent <a> appearing anywhere within <a> and so on?
I'm announcing it here because I hope the audience is fairly small but discerning, and I'm announcing it at all because I've run out of steam for the moment. This is the first code above the size of a nonce-programme that I've written since I got ill years ago, so don't go too hard on me!
I hope you won't consider my response hard ;-)
No; and if WASH /can/ now enforce all the restrictions but isn't generally used that way, I think that's a pity (and making it easier to find how to do this would be a big improvement).
Perhaps you could borrow some ideas from Peter's code, or vice versa.
It turns out that the mechanism I've used to enforce the restrictions is almost the same as the one he mentions in the thesis as being too awkward, except that I don't in fact need 98 type parameters, just fourteen... and I disagree with his statement that moving to xhtml means that implementing the restrictions is unnecesary -- W3C says that the informal description is the normative definition, not the DTD. Another difference is that I haven't used any non-Haskell 98 constructs other than using Template Haskell to generate class declarations and instances (were one so inclined, one could get ghc to output the splices and [clean them up by hand to] produce an entirely H98 version). -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk