Re: Conditional Text

[Hans Hagen <pragma@wxs.nl>]

At 11:24 PM 1/24/2003 +0100, you wrote:
>On Mon, Jan 20, 2003 at 10:07:45AM +0100, Hans Hagen wrote:
> > At 05:06 PM 1/18/2003 -0700, you wrote:
> > >Greetings!
> > >
> > >  Is it possible to have parts of the ConTeXt file
> > >processed conditionally? I'm hoping to be able to do
> > >something like:
> > >
> > >(in ConTeXt file)
> > >
> > >Question: What is the derivative of $e^{sqrt{x}}$\\
> > >\some-command-start
> > >Answer: $\frac{d}{dx} e^{sqrt{x}} ... $
> > >\some-command-end
> > >
>
>[...]
> >
> > \defineblock [answer]
> >
>
>Interesting: Three of your users suggest using modes instead. I would
>have too.

well, nowadays there is setups as well (more on that in some new styles)

>What made you choose blocks over modes here?

(1) no argument grabbing and therefore catcode save, which means that 
verbatim and so will work
(2) they keep track of numbering, so that when you call them up later (say 
in appendix) you can get similar numbers; say that you want a summary of 
formula's: put them in blocks, tag them (with optional arg you cna group 
them in subblocks), then, when you call such a subgroup you get proper 
numbers; also, refs in such recalled blocks know from which 
chapter/section/etc they come, so they will be prefixed accordingly
(3) hooks and local variables
(4) nesting is possible

[btw a pretty old mechanism, one of the reasons for context being there]

Hans
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