Re: Flush COMPILER-LET?

[sandra%defun@cs.utah.edu (Sandra J Loosemore)]

> Date: Tue, 27 Sep 88 12:15 EDT
> From: Kent M Pitman <KMP@STONY-BROOK.SCRC.Symbolics.COM>
> 
> 
> Also, the MACROLET version doesn't deal with the issue of
> side-effects. Offhand I see now way to use MACROLET to simulate a
> situation which uses COMPILER-LET and where a compiler-let variable is
> re-assigned (by SETQ) in a contained macro call. The kind of macro
> where you'd do that would be
> 
>  (WITH-MY-STICKY-DECLARATIONS
>    (+ (MY-THE FIXNUM X) (MY-SQRT X)))
> 
> where MY-THE might be like THE, but it could push onto a list of
> declarations maintained by WITH-MY-STICKY-DECLARATIONS so that MY-SQRT
> could be a macro that knew X was a FIXNUM.

This may or may not work anyway, even if COMPILER-LET is used.  Our
proposal for DEFINING-MACROS-NON-TOP-LEVEL explicitly states that you
can't depend on subforms being processed in the same order they appear
textually.  (This is to allow the compiler to perform certain kinds of
source-to-source transformations.) You can't rely on the MY-THE being
expanded before the MY-SQRT unless you have WITH-MY-STICKY-DECLARATIONS 
do its own code walk. 

-Sandra
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