> Let's try to keep at least this discussion at a technical level.

Sorry if I went overboard. Simplicity is one of the main technical
concerns in my book so it's difficult to stay neutral at times.

> At least from that point of view, the CL model doesn't seem to provide
> anything but syntactic sugar over an extra plist argument.

You are right:

(defun foo (&key a b c) (list a b c))

(apply #'foo '(:a 1 :c 3)) ; => (1 NIL 3)

Note that 177 has subtly different `apply` semantics than CL (more below).

> If the procedure `foo' is known at the call site, a good compiler can
> optimize a lot.  Even plist arguments encoding keywords can be handled
> in an optimized way.

Yeah, that's the scenario I was wondering about. Calls to unknown
procedures will have to use the slow path. But isn't that the case also
for Kawa/Racket-style kwargs? It may be able to omit some checks, but it
will still have to internally make a hash-table or list out of the
kwargs. I guess the callee can assume the keyword list is sorted/hashed
properly and doesn't need to type-check the keywords or the collection
containing them and their values.

> In general, `foo' is not known at the call site or `foo' is defined in
> some other module, for which no compile-time information is available.

Is it the usual case that the information isn't preserved across module
boundaries? I had assumed that at least the fastest compilers like
Gambit and Chez would preserve it.

> With the CL model, `foo' has to be treated as an ordinary procedure
> taking 4 arguments.  Otherwise, as I have described in my first post in
> this thread, section 4.1.3 of the R7RS-small would be violated.

That's correct as far as I can tell.

Since SRFI 177 works with both CL style and Kawa/Racket style, it cannot
guarantee that keyword arguments may be passed using ordinary `apply`.
The lack of this guarantee is a difference from CL.

However, 177 can guarantee that `apply` works when no kwargs (and no
arguments in rest position) are given. Though it cannot help with any
compile-time checks.