Subject: Re: On side effects From: "James Clark" <jjc@xxxxxxxxxx> Date: Wed, 18 Jun 1997 14:11:38 +0700 |
> From: Paul Prescod <papresco@xxxxxxxxxxxxxxxxxxxxxxxxx> > To: dssslist@xxxxxxxxxxxxxxxx > Subject: Re: On side effects > Date: Tuesday, June 17, 1997 11:35 PM > So you can think of the final flow object tree as a set of flow objects and > associated *expressions* that specify characteristics. Right. > You could imagine that > the expressions are all evaluted as a post-process step and then the flow > object tree is returned. While the DSSSL code itself is executing, it is > (theoretically at least) isolated even from its parent context. That's how > I understand it anyhow. > > I personally think that this level of firewalling is maybe a little > extreme, But given that inheritance happens in the flow object tree how can it be otherwise? Consider (let ((x (make sequence font-size: (+ (inherited-font-size) 2pt) (literal "foo")))) (sosofo-append (make paragraph font-size: 10pt x) (make paragraph font-size: 12pt x))) The make sequence expression gets evaluated once, but the expression specifying the font-size characteristic has to get evaluated twice with a different result in each case. James DSSSList info and archive: http://www.mulberrytech.com/dsssl/dssslist
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