Thanks for that explanation. Indeed, I found it hard to find a thorough
explanation anywhere. Also, thanks for reminding me about propertize.


On Thu, 23 Feb 2023 at 19:36, Stefan Monnier <monnier@iro.umontreal.ca>
wrote:

> > Indeed, I assumed that I was creating new strings because (eq " " " ")
> > is nil.
>
> Your test can return nil even if new strings aren't created at runtime
> (e.g. because each source code string gets its own runtime string).
>
> It may be nil in your test, but it may also return t (I think if you
> byte-compile your test it will return t).
>
> >> >         (let ((s " "))
>
> Here you have a single " " string in your source code.  And no it's not
> recreated each time, it will be the same one reused everytime (and
> modified by `put-text-property`).
>
> You can use `propertize` instead.
>
>
>         Stefan
>
>