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Re: Defmacro inside of a let
Date: Sat, 1 Feb 1986 10:13 EST
From: Rob MacLachlan <RAM@C.CS.CMU.EDU>
Subject: Defmacro inside of a let
That's because the compiler wants to be able to evaluate macros at
compile time. It would be impossible to compute the lexical
environment of a macro definition without actually interpreting the
surrounding code. This is basically impossible, and is almost
certainly not what you want. It is more obvious in the case of
MACROLET, which is usually embedded in random code somewhere. This is
explained to some degree on page 114.
I may be missing something here, but it seems to me that the compiler
wants to process ALL toplevel forms at compile time. Of course the
compiler would have to interpret the surrounding code to calculate the
lexical environment. I don't see why this is basically impossible. This
is exactly what was being discussed in the recent "Defun inside LET"
controversy. As for not being what the programmer wanted, what about
the person that wants to (for whatever reason) write the following:
(let ((counter 0))
(defmacro conditional-expand (...args...)
(if (< counter *some-level*)
I'm not defending this code, or even saying that this is the only way
to do such a thing, but what's wrong with it linguistically?