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Re: need for 'dynamical-let'?

From: David Kastrup
Subject: Re: need for 'dynamical-let'?
Date: Fri, 24 Jul 2015 06:40:34 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux)

"Stephen J. Turnbull" <address@hidden> writes:

> Stephen Leake writes:
>  > Can we define a macro 'dynamical-let' that would implement this
>  > pattern, but with hidden variables?
> First, was there a typo in your post?  add-to-list normally takes a
> (quoted) symbol.  Since the argument isn't quoted, it appears that the
> effect is that you are attempting to add-to-list to the variable (not
> the value!) nil.  Assuming that was a typo....
> `dynamical-let' is about as ugly as ugly can get, and anyway it
> shouldn't be necessary.  The variable is lexically apparent and its
> value is not magical in any way.  Your code *should* work.

add-to-list is a function (not a macro) taking a symbol as indicator of
a variable.  So lookup happens at run time when the lexical environment
is already gone.  No way this can happen lexically.

David Kastrup

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