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From: Per Bothner <>
To: Panicz Maciej Godek <>,
Subject: Re: Type information seems to be erased in macros
Date: Wed, 29 Dec 2021 15:30:09 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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.

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.
	--Per Bothner

  reply	other threads:[~2021-12-29 23:30 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 [this message]
2021-12-30  8:52   ` Panicz Maciej Godek

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