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Re: [Gnu-arch-users] Re: Pika 0.1pre3 -- writer, vectors, contributions

From: Jonathan Walther
Subject: Re: [Gnu-arch-users] Re: Pika 0.1pre3 -- writer, vectors, contributions
Date: Fri, 28 Nov 2003 01:03:06 -0800
User-agent: Mutt/1.5.4i

On Fri, Nov 28, 2003 at 05:46:44PM +0900, Miles Bader wrote:
Jonathan Walther <address@hidden> writes:
Since macro side effects can be useful, why make a person go through
contortions to obtain them?  I can see maybe adding some syntactic sugar
to make such side effects intentional, but why try to eliminate them

I thought that's what hygienic macros _were_ -- syntactic sugar to make
sure macros do what they look like they're doing, but also allowing the
full power of traditional lisp macros; my vague recollection is that
it's not particularly hard to declare certain arguments as being
`untouchable' (I mean simply included as-is, without hygiene).

Alas, that isn't how R5RS defines hygienic macros.  If you were to
implement just R5RS, you would end up with hygienic macros that provide
no simple or easy way to go unhygienic, that is, no simple way to do
variable capture.

The contortions needed to do variable capture in R5RS are elephantine
enough that they are not practical for normal use.

Chefs still use big sharp kitchen knives without any safety guards; the
key is, they know how to use them, and are very fast and effective with
them.  If you want to cut something, you need a sharp blade, and there
will always be a risk.  The key is finding the appropriate balance
between risk of cutting yourself, and efficiency in getting the cutting
job done.



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