Subject: Re: DSSSL side effect-freeness From: Pierre Mai <dent@xxxxxxxxxxxxxxx> Date: 28 Jan 1998 18:39:40 +0100 |
>>>>> "FAC" == Frank A Christoph <christo@xxxxxxxxxxxxxxxxxx> writes: FAC> So, recalling that laziness does not mix well with side FAC> effects, you can see that there are usually two extremes for FAC> a functional language: either it uses CBV and has FAC> side-effects, or it uses Need and has no side-effects. FAC> Clearly both alternatives have their advantages. FAC> But now consider the DSSSL expression language. In the world FAC> I have just drawn, it is a very strange beast indeed: it FAC> isn't lazy and it hasn't got any side-effects. This puts it FAC> smack in the middle of two Good Things, yet possessing FAC> neither, like a child at Christmas that can't make up its FAC> mind about which present to open first. I'd just like to point out, that there are a number of pure functional, yet non-lazy (i.e. eager) functional languages, e.g. Opal, developed locally at the Technical University of Berlin, see http://uebb.cs.tu-berlin.de/~opal/. Apart from eagerness being easier to implement, it usually leads to language implementations that have less state to carry around with them. Currently, this _can_ lead to faster execution times and/or smaller memory footprints than implementations of lazy languages achieve, although they should theoretically be faster/more efficient... Especially the interaction possibilites with "current-*" in groves might lead to much state being carried around, though this is only speculation on my part... On the whole I rather think, that the decission for eagerness was probably mostly carried by the arguments for simplicity and/or compatibility with the Scheme way of things, rather than by theoretical considerations for speed and equivalence... Also I wonder if it would not still be possible (even if not really standard-conformant) to implement DSSSL in a lazy way, and probably most Style-Sheets would continue to work unchanged... FAC> distributed, though -- and I can't imagine distributed groves FAC> being a typical case anyway. Well, if we look at the corporate world, where large technical document repositories are being maintained and deployed as IETMs for example, I would rather think that distributed groves might be heavily used... Just my two centieuros... Regs, Pierre. -- Pierre Mai <dent@xxxxxxxxxxxxxxx> http://home.pages.de/~trillian/ "Such is life." -- Fiona in "Four Weddings and a Funeral" (UK/1994) DSSSList info and archive: http://www.mulberrytech.com/dsssl/dssslist
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