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: Michael Heerdegen <michael_heerdegen <at> web.de>
Cc: 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: Wed, 31 May 2017 20:02:30 -0600

Michael Heerdegen <michael_heerdegen <at> web.de> writes:

> With print-circle and print-gensym bound, I think the result does not
> really read worse than how it would look like with with `cl-gensym'
> generated code.

That's much better, though I still think it could/should be better. For
example, if you have multiple uninterned symbols with different
symbol-names, they're all referenced by #number, and use the same
counter.

It also seems to make the output uglier as well. Consider:

(macroexpand '(cl-loop for x in '(1 2 3)
                       for y in '(a b c)
                       repeat 10
                       repeat 20
                       collect (list x y)))

Note the expressions using #5#. I suppose the 0 is being shared.

It would also be nice if instead of many --cl-var-- variables,
particular clauses would result in different symbol-names. For instance,
if the `repeat' clause made a symbol called --cl-repeat--. This would
further help readability.

Also, using gensym could help 3rd-party packages. I usually use
macrostep to expand macros and the value of print-circle has no effect
on its expansions. macrostep individually prints out each uninterned
symbol using prin1; can this approach be easily modified to get the same
result as macroexpand?

PS: The first line of the documentation of print-circle only mentions
that it affects recursive structures. Perhaps it should mention the
"shared substructures" part in the first line for emphasis?

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