bug#29866: 27.0.50; cl-loop: Calculate the array length just once

[Tino Calancha <tino.calancha@gmail.com>]

On Wed, 27 Dec 2017, Stefan Monnier wrote:

>> X-Debbugs-CC: monnier@iro.umontreal.ca
>
> Thanks.
>
>> It looks sensible to calculate the array length just once,
>> instead of recalculate it on each iteration:
>
> I tend to agree, but I don't know very much about the intended semantics
> of Common Lisp's `loop` macro, nor about cl-loop's implementation (tho
> I admit I did mess with it without being really sure what I was doing).
While studying this code I found easier to hack if we use gensym's
instead of make-symbol; otherwise, the code creates several symbols with
the same printed representation "--cl-var--".  For example, with 
current code you can read expansions with something like:

(let* ((--cl-var-- 'foo)
        (--cl-var-- 'bar))

I prefer to read:

(let* ((--cl-var--1 'foo)
        (--cl-var--2 'bar))

Do you have any preference in these cases?