Functional Programming with XSLT – A proof through examples
This paper sets out to show that XSLT is a true functional language, by implementing 35 of the most common functions that you would encounter in such a language (foldl, map, minimum, sum, sumTree etc)! It’s long (the PDF version is 76 pages) – mostly because of the code: just because XSLT can implement all these things, that doesn’t mean it’s easy, simple, elegant or clean!
I’m enjoying playing with the new musicdatabase chain of CDDB data -> MySQL -> SQL -> Class::DBI -> FireCore -> Template::Toolkit -> XML -> XSLT -> HTML -> CSS -> display, but XSLT is jumping out as by far the most verbose, ugly, and unreadable link in that chain. It hasn’t been around enough yet, or been used widely enough yet, for there to be much written on on the speed/cost of development, or maintainability.
In theory, the really complex stuff should be sufficiently abstractable to allow for building up quite powerful libraries. Although XSLT doesn’t support higher order functions directly, it’s possible to simulate them, as this paper (and its examples) shows. If this sort of thing can be turned into a “sufficiently encapsulated hack”, then it may indeed be possible to write XSLT relatively quickly and neatly.
