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Re: [PATCH] Unicode Lisp reader escapes

From: Stefan Monnier
Subject: Re: [PATCH] Unicode Lisp reader escapes
Date: Fri, 05 May 2006 09:05:15 -0400
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (gnu/linux)

>> > ??? inside the Lisp reader, everything needs to be fast, IMO.
>> Why?
> Because the Lisp reader is the backbone of the Lisp interpreter.

>> IMO the only things that need to be fast are those things whose
>> performance has a visible impact.  I see no evidence that there'll ever be
>> a case where the speed with which we can read \u escapes will matter.
> You don't need to see an evidence of a collapsing bridge to know that
> it must be several times stronger than any imaginable load that could
> ever be put on it.

We're talking performance here, not correctness.

> In other words, not everything is empirical; there's a thing called
> ``good engineering practice.''

And we're talking about a micro-optimization, not an algorithmic
optimization, so the only good engineering principle I know in this domain
is: don't micro-optimize before you know it's necessary.

> Sorry for being overly didactic, I'm sure you know all that.  I'm just
> amazed that such a fundamental issue needs evidence.

I don't need evidence to accept the C code version, but I need such evidence
before I can accept "performance" as the motivation for the use of C code
rather than elisp.


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