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

[João Távora]

On Sat, Nov 11, 2023 at 6:12 AM <tomas@tuxteam.de> wrote:
>
> On Sat, Nov 11, 2023 at 09:23:26AM +0800, Po Lu wrote:
> > Dmitry Gutov <dmitry@gutov.dev> writes:
> >
> > > Just to take this example, there are about 2 major bugs: 1) the list
> > > will come out reversed, 2) the code does XOR rather than subtraction.
> >
> > Hmm, reading its doc string, I think a more illustrative name for
> > cl-set-difference would be cl-set-complement.  In this case, the second
> > loop can be removed.
>
> Yes, "difference" is, surprisingly, ambiguous.

I wouldn't say "ambiguous", but this page has a brief review of
different ways the operation is referred to in literature.

   https://proofwiki.org/wiki/Definition:Set_Difference/Also_known_as

In programming languages "set difference" seems to be the
overwhelmingly established term

  https://cplusplus.com/reference/algorithm/set_difference/
  http://clhs.lisp.se/Body/f_set_di.htm
  https://docs.python.org/3/library/stdtypes.html#set
  https://ruby-doc.org/core-1.9.3/Array.html#method-i-2D
  
https://doc.rust-lang.org/std/collections/struct.HashSet.html#method.difference

> Your implementation is
> usually called "symmetric difference" to avoid that.

Correct.