Re: [Chicken-users] On parameterize and fluid-let

[Kon Lovett]

On Oct 14, 2007, at 5:39 AM, Tobia Conforto wrote:

> Hi all,
>
> I'm new to Scheme and to Chicken, and I like what I see so far!
>
> Question: does (parameterize) have any hidden or special meaning  
> that's
> not obvious?  Are these two forms equivalent, except maybe for the
> introduction of a few symbols?
>
> (parameterize ((param1 value1) ...)
>   body ...)
>
> (let ((old-value1 (param1)) ...)  ;save parameters
>   (param1 value1) ...             ;change parameters
>   (let ((ret (begin body ...)))   ;execute body and save return value
>     (param1 old-value1) ...       ;restore parameters
>     ret))                         ;return value
>
> Is (parameterize) just a handy macro for the latter form?

Yes.

> As far as I can see, the only difference could arise in multi- 
> threading
> (which I haven't studied yet, in Chicken) but parameters are already
> supposed to be thread-local, so I'd wager they really are the same.

Yes.

> (fluid-let), on the other hand, operates on non-thread-local  
> variables,
> so its effect is very different from these two forms.  Is this  
> correct?

Yes.

> Tobia
>
>
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Best Wishes,
Kon