GNU bug report logs - #27177
26.0.50: Macroexpanding cl-loop and friends (make-symbol usage)

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From: Alex <agrambot <at> gmail.com>
To: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
Cc: Michael Heerdegen <michael_heerdegen <at> web.de>, 27177 <at> debbugs.gnu.org, npostavs <at> users.sourceforge.net
Subject: bug#27177: 26.0.50: Macroexpanding cl-loop and friends (make-symbol usage)
Date: Sat, 03 Jun 2017 18:24:36 -0600

Stefan Monnier <monnier <at> IRO.UMontreal.CA> writes:

>> Stefan, why did you make the switch? Using cl-gensym would help a ton
>> with readability of cl-loop's macroexpansion.
>
> I don't consider human-readability of the result to be something that
> a macro should have to pay attention to.

I can understand that when talking about smaller macros, but loop is a
fairly complex macro, so I believe human-readability is a desirable
trait to have if feasible. It would help with debugging and overall
understanding of cl-loop.

I've browsed around for a few common loop implementations and they all
use gensym (CCL uses gentemp) and descriptive naming:

SBCL: https://github.com/sbcl/sbcl/blob/master/src/code/loop.lisp

CLISP: https://sourceforge.net/p/clisp/clisp/ci/default/tree/src/loop.lisp

CCL: https://github.com/Clozure/ccl/blob/master/library/loop.lisp

ABCL (admittedly they adapted it from SBCL):
http://abcl.org/trac/browser/trunk/abcl/src/org/armedbear/lisp/loop.lisp

I also found a CHICKEN Scheme egg for CL's loop, and it uses gensym (but
generic names, unfortunately).

If there's a good reason to not use gensym, then that's fine, but if the
problem is easy enough to work around (perhaps per-expansion counter so
that it will never realistically hit most-positive-fixnum), then I think
cl-loop should use it.

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