bug#47425: 26.3; `plist-get', `plist-put' should accept a TEST function

[Drew Adams]

> But the point is that alists has several more advantages: counting
> number of keys is twice as fast, iterating and/or transform the
> collection easily done with mapcar, mapcan, dolist, mapc etc. Plists
> have no real advantage from their structure.

Alists have a zillion advantages over plists.

That's not what this enhancement request is about.

A similar situation exists between vectors and
lists.  And even among different numeric types.
And even between Lisp symbols and strings.

It's the case that sometimes users use a type
that's less useful than another type in some
context.  That's irrelevant to whether plist
functions could benefit from a TEST arg.  IMO.