Re: What's missing in ELisp that makes people want to use cl-lib?

[João Távora]

On Wed, Nov 15, 2023 at 1:07 AM João Távora <joaotavora@gmail.com> wrote:

> Not really.  Only if I use my seq in contexts where I need that
> generic, and being second argument to seq-difference doesn't count.
> So why should I bother implementing that when my code is working
> fine today?
>
> But say I did that seq-do, then what is the seq-contains-p generic good
> for then?

Let me answer that for you... It could be, maybe even likely, that the
code was trying to get out of seq-do for some types of operation, because in
the case of lazy lists, seq-do would mandate the list be completely expanded.

So, while the code works, you seq-difference-3 now calls seq-do on the
second argument, and kills my laziness, naughty naughty.

Actually for this point to make sense, it doesn't even have to be
a bizarre voodoo list.  The lazy list may just be expanded enough already
for me to know in seq-contains-p that there's a given element
there without having to call the generator for more list elements.

So seq-contains-p was indeed an optimization, in more or less
the sense you described, which is now lost when you tried to optimize
for bare Lisp sequences.

João