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From: Panicz Maciej Godek <>
To: Per Bothner <>
Subject: Re: Type information seems to be erased in macros
Date: Thu, 30 Dec 2021 09:52:12 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi! Thanks for quick reply!

czw., 30 gru 2021 o 00:30 Per Bothner <> 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:

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

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

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

Thanks again!

      reply	other threads:[~2021-12-30  8:52 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-29 22:12 Panicz Maciej Godek
2021-12-29 23:30 ` Per Bothner
2021-12-30  8:52   ` Panicz Maciej Godek [this message]

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