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Re: Macro uexpansion

From: Jim Blandy
Subject: Re: Macro uexpansion
Date: 19 Dec 2000 14:59:38 -0500

I have to say:

a) macros which are powerful enough to run arbitrary code to determine
   the expansion, and

b) an evaluation framework which doesn't tell you whether, when, or how often
   an expansion will happen

seem fundamentally irreconcileable to me.

If I cannot control when expansion will happen, then the flexibility
a) offers is useless, because I can't reliably use it.

If I can write macros that run arbitrary code at expansion time, then
it must be apparent when that expansion will happen.

This is exactly the kind of unfortunate coincidence of 'flexibilities'
that Craig is warning us about; he's telling us that the CL community
found this to be a serious problem.

Mikael, it sounds like this doesn't bother you, which I consider a
serious gap between us.  If we don't share some common understanding
on something so fundamental, I'm not sure we're ready to discuss
details yet.

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