bug#12314: 24.2.50; `add-to-history': use `setq' with `delete'

["Drew Adams" <drew.adams@oracle.com>]

> > Eli, at the risk of butting in, I respectfully suggest that 
> > you might not be reading about this topic well enough or
> > perhaps not thinking enough about it.
> 
> How is this remark helpful?

I am sincerely _trying_ to help you.  I've tried to explain and give examples.
I've pointed you to other explanations on line and elsewhere in the Elisp
manual.  And I've suggested that you take a bit more time to study and think
about what you've read.  And I would add, perhaps experiment.

If my attempts to help do not help you or you do not appreciate them, sorry.

This is really not that big a deal.  Ask around.  This is a common question and
lots of people have explained it in various ways.  Take your pick.

> > Stefan is making the point that when programmers use 
> > `delete' or `delq' or `nconc' they often do so to improve
> > the performance of their code.  Which is true.
> 
> This is an entirely different issue.  "Destructive modification" does
> not imply the optimization you (and evidently Stefan) are alluding to,
> at least not universally so, nor a possibility to piggy-back that to
> optimize application code.  It just means that the original object is
> modified (a.k.a. "destroyed") in the process.

To quote a famous person (you), I give up.  I sincerely hope someone else helps
you find what you're looking for.  If not, maybe you will reread the thread or
the manual at a later date and you will find it yourself.  Sometimes that's all
it takes for things to become clear.