[slime-devel] Re: ABCL patches for SLIME HEAD

[Mark Evenson]

Tobias C. Rittweiler wrote:

> Just a guess, but what I could imagine that
> `parse-first-valid-form-spec' in swank-arglist.lisp could possibly be
> the culprit, as it uses the "mapping on several lists, one being
> circular" trick: 
> 
>   (mapcar #'+ '(1 2 3 4) '#1=(10 . #1#))
> 
> I'd expect this one to return (11 12 13 14), but closely rereading the
> CLHS entry for the mapping functions, reveals that those are actually
> only defined for /proper lists/.

Actually, ABCL seems to handle this form ok, returning the expected (11 
12 13 14).  And ABCL can compile PARSE-FIRST-VALID-FORM-SPEC from 
swank-arglist.lisp.

The problem ABCL seems to be once again [1] in its MOP when it attempts 
to compile the DEFMETHODs for EXTRA-KEYWORDS with the first argument 
specialized on (EQL 'MAKE-INSTANCE).

The following blows ABCL up with an unprintable (by SLIME) backtrace:

;;; From SLIME 'contrib/extra-keywords.lisp' r1.5

(defgeneric extra-keywords (operator &rest args)
    (:documentation "Return a list of extra keywords of OPERATOR (a
symbol) when applied to the (unevaluated) ARGS.
As a secondary value, return whether other keys are allowed.
As a tertiary value, return the initial sublist of ARGS that was needed
to determine the extra keywords."))

(defmethod extra-keywords ((operator (eql 'make-instance))
                            &rest args)
   (multiple-value-or (apply #'extra-keywords/make-instance operator args)
                      (call-next-method)))


> 
> Is this something one could (and should?) reasonably expect to be de
> facto portable behaviour? IOW, am I to blame, or is ABCL?
>

I don't really feel qualified to answer about portability:  all I can 
offer is that ABCL seems to understand the idiom correctly, but I 
haven't looked at the relevant code in the reader.


[1]:  See the discussion around 
http://thread.gmane.org/gmane.editors.j.devel/1397 for context.

-- 
Mark Evenson <evenson at panix.com>

"A screaming comes across the sky.  It has happened before, but there is
nothing to compare to it now."