Re: Type information seems to be erased in macros

[Panicz Maciej Godek <godek.maciek@gmail.com>]

Hi! Thanks for quick reply!

czw., 30 gru 2021 o 00:30 Per Bothner <per@bothner.com> napisał(a):

>
>
> On 12/29/21 14:12, Panicz Maciej Godek via Kawa wrote:
> > Does the macro system erase type information from objects?
>
> Not in general, but it is possible that a compond name
> like screen:translate! might not survive the macro-expansion process.
>
> The --debug-print-expr flag may be useful to see what is happening.
> It prints out the syntax tree after name lookup and macro-expansion,
> but before type analysts and optimizations.
>
> It you post a short self-contained program I can take a look.
>
> Actually, this turned out to be a trivial mistake on my part -- the name
"screen" wasn't visible as I thought it was.


> There is a good chance you might have better luck with:
>
>      (invoke screen 'translate! x! y!)
>
> That should avoid any issues with compound symbols.
>
> > If I add explicit casts in the macro, is it likely to cause some
> > performance penalty?
>
> Almost certainly nothing you'd notice: Probably just an extra checkcast
> instruction in the bytecode.  Which means some extra work, but pretty
> minor.
>
> If end up needing run-time reflection (which is what you get if
> you ignore the warning), that is a lot more expensive.
>
>
Thanks, that's good to know!

BTW I've been working on a touch-based Scheme editor for Android called
GRASP, and I managed
to hook up Kawa to it, which gave a nice effect:

https://www.youtube.com/watch?v=oOHg74HYau4

I also gave an overview of GRASP during this year's Scheme Workshop (before
integrating with Kawa)

https://www.youtube.com/watch?v=FlOghAlCDA4

The source is available here (the structure of the repo is a bit tricky, so
I can explain it if anyone's interested)

https://github.com/panicz/grasp-android

Currently, I am in the process of rewriting GRASP to Kawa, because I find
it much more comfortable to program in.

Thanks again!