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Re: need for 'dynamical-let'?

From: Stephen Leake
Subject: Re: need for 'dynamical-let'?
Date: Fri, 24 Jul 2015 02:58:09 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (windows-nt)

"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.  

Yes, that's 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 uses 'symbol-value' on the quoted symbol. As David Kastrup
points out, and as symbol-value doc string says, that does not see
lexical values. So the code will not work.

> Or, perhaps, as Dmitry and the add-to-list docstring suggest, you
> should convert the code to use `push' or `pushnew' instead.  

I was working in Emacs 24.3, where the add-to-list doc string does not
mention "push". But the Emacs master doc string does mention it.

> The inconvenience of the busybody compiler macro may be considered a
> "feature" intended to encourage you to modernize your code.


-- Stephe

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