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From: Krzysztof Drewniak on 5 May 2010 19:04
On 2010-05-05, Captain Obvious <udodenko(a)users.sourceforge.net> wrote:
> KD> While sitting in class bored (I know, great passtime) I had an
> KD> idea. Functions would work great especially if there was a dynamic-let
> KD> (or something) which would work just like let but create variables
> KD> that are dynamic, not lexical. For example:
> KD> (defun foo ()
> KD> (dynamic-let ((x 3))
> KD> (funcall #'(lambda () (print x)))))
> KD> and (foo) would print 3. However, I have no idea how to *write* such a
> KD> macro. Dang. Any help?
>
> It is simple:
>
> (let ((x 3))
> (declare (special x))
> ...)
>
> will create a dynamic variable binding.
>
> However, to be fully standard-compatible, you need to declare them special
> in your function too.
>
> E.g.
>
> CL-USER> (defvar *foo* (lambda ()
> (locally (declare (special x y))
> (+ x y))))
> *FOO*
> CL-USER> (let ((x 3) (y 5)) (declare (special x y)) (funcall *foo*))
> 8
>
> But it works even if you do not declare them special in most
> implementations, might produce warnings, though.
>
This will work. I guess I'll just have to put up with it. Thank you
for all the help ovwer these last few days. *gets back to coding work*

Krzysztof Drewniak

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