Re: Updated Guile Tutorial

[Daniel Kraft]

Hi Andy,

thanks for your comments and checking over my revised tutorial!

Andy Wingo wrote:
> A few comments, IMO of course. Neil probably has a better perspective.

I agree with you in general on those, and will try what I can improve on 
them; so please wait with a commit in any case ;)  Should I think that 
the current version is best of all my trials, I'll also let you know...

>  1) It would be better to have a more neutral narrator -- not a
>     first-person narrator. If you feel like you need to speak from the
>     first person, use "we". OTOH your style is infectious :), so perhaps
>     it would work as "Guile Tutorial, by Daniel Kraft" :)

That's something I usually also try to achieve in writings "like that" 
-- however, I liked the original's style and tried to get my own version 
in the same spirit.  Here, I'm not sure if I can get rid of first person 
entirely; and I think I tried to use "we" wherever possible, but for 
stuff like "I wanted to use Gtk+ but resided finally to Gnuplot 
because..." I'm not sure how to do this; overall, it's really meant from 
the author's perspective and not something like "we're going to do that 
now".

I'll still try to work over the text when I find time and maybe I can 
reformulate it -- concrete suggestions are welcome, if you stumble upon 
certain passages, of course.

>  2) Don't mention the history of the tutorial. Just have it be a current
>     document.

I wanted to give credits to the original author, but you're right that I 
should probably move this to some concluding section.  As you make me 
think about that, I also need to add a GNU FDL note somewhere.

>  3) In general, use short sentences. Let your words breathe.

Ok, I'll see what can be done there; I just fear that this is a 
remainder of German being my native language, so I'm usually not content 
with short sentences...

>  4) If you're forking to run gnuplot, why not do so from Scheme? Of
>     course if you did that it would obviate the whole "extending C"
>     story, but still, if given this particular problem, that's what I'd
>     do.

I've never tried this actually myself, but I think it would not be too 
hard to implement all of this in Scheme alone; but as you mentioned, I 
just needed something to write in C ;)

But if you've got a suggestion as what I could reasonable still change 
(maybe some final remarks that this example would also be possible in 
Scheme) I'll consider it.

>  5) Running a main loop (as gtk+ does) and a REPL is indeed an
>     interesting problem. See event-repl.scm or graphical-repl.scm in
>     guile-gnome for a couple of takes.

I imagine the "correct" solution would be to start the REPL in a 
seperate thread and do drawing by updating some shared data structure 
that is read and rendered from the Gtk+ loop's exposed-callbacks; or 
something alike.

This shouldn't be too hard if we wanted to implement a clean program 
anyways, but for means of the tutorial I think the current version is 
better.

>  6) I wish we had a better Scheme->C story; our C->Scheme story is fine,
>     but a better FFI would be nice.

I'm not sure about that...  For all I did so far, the Scheme->C stuff I 
regard also as quite good.  The only thing is that you need to write 
wrappers for each function; so maybe we could try to get a FFI where you 
can just define the interface of a C function and Guile does the SCM 
boxing/unboxing accordingly on calls.  Are there already plans (or at 
least the concrete desire) to do stuff like this?  I think at least for 
some very basic functionality it should not be too hard to do?

Cheers,
Daniel

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