check-keyword-arguments

[David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>]

    Date: 19 May 88  1613 PDT
    From: Dick Gabriel <RPG@SAIL.Stanford.EDU>

    I want to present one more alternative to the initargs checking
    problem.

[Getting rid of check-initargs & successors, writing the code inline,
and putting it in chapter 3.]

This sounds good to me, with a couple modifications suggested below.
Let's go with it.

    We could introduce a new generic function called valid-keywords, which
    takes an object; if it is something with keywords (like a generic
    function, a method, or a function), valid-keywords returns two values: a
    list of the explicitly named keywords and a boolean which states whether
    &allow-other-keys had been specified in the definition.

function-keywords would be a better name.  Otherwise okay.
I have no quarrel with the dual return values.
[Yes, I know (subtypep 'method 'function) => nil t.  Nonetheless,
in this context the method is used in a functionesque way.]

I assume method-applicable-keywords, p.27 of the most recent draft
of ch.3 that I've seen (the one handed out at X3J13 in March), would
go away.

    Then we could write make-instance like this:

    (defmethod make-instance ((class standard-class) &rest initargs)
      (setq initargs (default-initargs class initargs))
      (let* ((proto (class-prototype class))
	     (methods 
	       (union
		 (compute-applicable-methods #'allocate-instance `(,class))
		 (union
		   (compute-applicable-methods #'initialize-instance `(,proto nil))
		   (compute-applicable-methods #'shared-initialize `(,proto))))))

I think you want append rather than union, since there won't be any
methods in common between distinct generic functions.  Also the args for
initialize-instance and shared-initialize have accidentally gotten
interchanged.

	    (unless
	     (subsetp
	      (let ((keys '()))
		   (do ((plist initargs (cddr plist)))
		       ((null plist) keys)
		       (push (car plist) keys)))
	      (union 
		(class-slot-initargs class)
		(reduce #'union (mapcar #'valid-keywords methods))))
	    (error ...)))
      (let ((instance (apply #'allocate-instance class initargs)))
	(apply #'initialize-instance instance initargs)
	instance))