Re: Appending lists

[Stefan Monnier]

tomas@tuxteam.de [2021-06-16 17:11:01] wrote:
> On Wed, Jun 16, 2021 at 10:22:23AM -0400, Stefan Monnier via Users list for
> the GNU Emacs text editor wrote:
>> tomas@tuxteam.de [2021-06-16 09:28:19] wrote:
>> > Doing (foo x y) will *never* change "the variable x" -- unless
>> > foo is a macro/special form.
>> 
>> Just to show that you should never say never:
>> 
>>     (let* ((x 5)
>>            (y 6))
>>       (cl-flet ((foo (a b) (setq x (+ a b) y (* a b)) (- a b)))
>>         (list (foo x y) x y)))
>
> Hey, that's cheating :-)

Impredicativity is borderline, indeed.


        Stefan