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

[João Távora]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> João Távora <joaotavora@gmail.com> writes:
>
>> This is all interesting, until one ponders what happens if an existing
>> seq.el user somewhere has:
>>
>> (cl-defmethod seq-contains-p ((seq my-voodoo-seq)
>>                               (elt (eql :secret-voodoo)) &optional _tesfn)
>>   (invoke-voodoo-priests seq))
>>
>> making use of seq.el's support for abstract polymorphic sequences.
>>
>> With seq.el 2.24 a seq-difference operation would consider this user's
>> method, with seq.el 2.24.dmitry (i.e. your fast seq-difference-3) it 
>> simply won't.  This user's code is clearly broken.
>
> It is debatable whether the result of such a seq difference is even well
> defined with the information you provided to Elisp:

Yes, of course: that's why I called it "voodoo".  It was just for the
sake of argument, and made Dmitry aware of a serious performance bug
that happens in much more legitimate* cases. The fix to that bug, while
it exists to a great extent (it's seq-difference-3 in Dmitry's patch or
branch feature/cl-lib-improvements), requires incompatible lisp changes,
hence proving my point that a bunch of generics thrown together does not
a good library make.

Anyway, read my latest mail to Dmitry.

João

[*] For some meaning of "legitimate", of course, but I think sparse
sequences are a good legitimate, for example.  seq.el's documentation is
where?  I don't see it.