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Re: goops and memoization
From: |
Lynn Winebarger |
Subject: |
Re: goops and memoization |
Date: |
Tue, 3 Dec 2002 12:17:36 -0500 |
On Tuesday 03 December 2002 02:59, Mikael Djurfeldt wrote:
> Well, actually we have a guarantee that when we re-memoize, 'lambda,
> 'if etc are bound to exactly the same thing as when the procedure was
> originally memoized. This is because the lexical environment of the
> method is used when re-memoizing.
Either define-syntax or define can change the meaning of
lambda in the global environment. It will use the same binding,
true, but that's not the same thing.
> Note that for method optimization to work, unmemoization *must* be
> faithful to the semantics of the procedure. The optimizer must be
> able to lookup the true binding of every identifier.
The memoizer is not an optimizer. It merely expands macros
into a constant core representation. I fail to understand the problem.
The internal constants are precisely what you want - a representation
of core scheme (plus some things like "and" and "or" that are
syntactic sugar but implemented for speed). They're not pointers
into a run-time symbol table, but so what? It's easy to translate
them to symbols for printing purposes.
> Thus, we have the requirement that memoization is semantically 100%
> reversible. Then one might of course argue that that is a too strict
> requirement.
Requiring reversibility of arbitrary macro expansions is pretty
close to nuts.
> The original reason for the choice to work on Scheme code instead of
> on the memoized representation was that it was simpler and could be
> handled on the Scheme level, and could be made to work quickly.
If you do it at the scheme level, sure. But if you're doing it at the
C level you have to use some system-specific representation anyway.
So what's wrong with constants?
Lynn
Re: goops and memoization, Mikael Djurfeldt, 2002/12/03
Re: goops and memoization, Mikael Djurfeldt, 2002/12/03