... 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. I thought to myself that this might make an undergraduate project, but then I thought "maybe it's too hard? I'd better write some of it to see how hard it is." After a while I decided that it was probably a bit too big for an undergraduate project, but by that time I'd written too much of it to throw away, and just had to keep going so here it is. 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 still am ill, so don't expect swift responses either. I'm mainly interested in opinions on the questions below, and in test cases that fail validation. You can get it with darcs get --partial http://homepage.ntlworld.com/jon.fairbairn/Typeful/Text/HTMLs and the documentation (such as it is) is at http://homepage.ntlworld.com/jon.fairbairn/Typeful/Text/HTMLs/Documentation/... Here's the announcement (which might better be called the release note, except that I'm not sure this counts as a relase). ------ Typeful HTMLs library Library of types and combinators to produce valid xhtml 1.0 (and eventually html 4.01) -- if you use this library (and if it's not faulty), you won't need to run the validator over the output of your code. Types prevent invalid nesting of elements (including the prohibitions of appendix B of the xhtml standard) and ensure an attribute is only passed to elements that has it. Most attributes are given types that reflect their content rather than just being strings (although some are just wrappers around strings for the moment). Includes full set of xhtml character entity names Includes type with names for all IANA-registered character sets. Provides the option of generating output in a choice of character sets (currently with the wide choice of utf_8, us_ascii, latin1 or iso_8859_5 (cyrillic)). Provides the option of generating xhtml without an xml version declaration (to avoid putting IE into quirks mode). It's generated by TemplateHaskell, but otherwise Haskell98. Questions: * I want to add a function to produce HTML 4.01. Unfortunately there are trivial differences (body takes a nonempty list in HTML but an ordinary list in xhtml, and similar). One approach (and the one I'd choose if left to my own devices) would be to restrict the document tree to the common subset, so the types would be constrained by whichever language was the more restrictive in any given case. An alternative would be to transform the xhtml tree by adding empty div elements. Which do people prefer? * Having a monad inside the result types of the *_allowed_in classes complicates the types, complicates programmatic generation of elements and makes some error messages much worse. It wouldn't be necessary if we simply wrote Haskell lists instead of using the +++ operator, ie instead of body << (h1 << ... +++ p << ... +++ p << ...) we had to write body << [h1 << ..., p << ..., p << ...] Admittedly, it is rather more awkward for nonempty lists: ul << (li <<... +++ li<< ... +++ li<<...) would have to be written ul << (li<<... +:[li<<...,li<<...]). Would anyone really be bothered by that? (Either that, or can someone come up with a way of rearranging the types so that +++ works without the monad in the result types of elements?) * What should I do about REQUIRED attributes? Some alternatives are listed in the TODO file. * The preference carrying monad used for Render is backwards; I tried making it go forwards, but the Laziness test programme took about 1.7 times as long to run. I'd like to put some state in there, which can't be done backwards. Can I do this somehow without the performance hit? * This pre release has a very restrictive license (barely falling short of "You may not use this!") My preference is, I think, to release it under LGPL. Is that going to cause people undue grief? -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk