From: "Stephen J. Turnbull" <stephen@xemacs.org>
To: Thien-Thi Nguyen <ttn@gnuvola.org>
Cc: emacs-devel@gnu.org
Subject: Re: emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...)))
Date: Wed, 05 Jan 2011 13:16:51 +0900 [thread overview]
Message-ID: <87zkrggf2k.fsf@uwakimon.sk.tsukuba.ac.jp> (raw)
In-Reply-To: <87tyhot4q4.fsf@ambire.localdomain>
Thien-Thi Nguyen writes:
> Sure, why not? Good fences make good neighbors, and the price
> of this flexible neighborliness (or neighborly flexibility) is
> syntax.
>
> (cond
> ((integerp x) => #'-) ; takes value
> ((not (listp x)) 42) ; traditional
> ((cdr x) => #'car) ; takes value
> ((car x) ; takes value, unnecessarily
> => (lambda (head)
> (code that ignores ; head
> oh well
> life goes on))))
Well, it makes me want to gag, that's all. ;-) I would not mix the
two, though (if the change is approved) you are welcome to do so.
After all, if you want the very occasional constant,
(applicating-cond
((integerp x) #'-) ; takes value
((not (listp x)) (lambda (y) 42)) ; constant function of 1 arg
((cdr x) #'car) ; takes value
((car x) ; takes value, 'cause that's how
(lambda (head) ; applicating-cond works, OK?
(code that ignores ; head
oh well
life goes on))))
Or (this is pretty disgusting, too) applicating-cond could check for
(functionp (cadr clause)), and call the function on the result of (car
clause) if that is non-nil, otherwise, return the value. I suppose
'#'car would make it possible to return #'car in that case.
> - Use a number to encode arity.
> N (EXPR N-ARY-FUNC)
>
> I think the last one is too strange, personally, but there it is.
The expansion could also use apply instead of funcall, so that the
function can be any-ary.
next prev parent reply other threads:[~2011-01-05 4:16 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-02 21:45 emacs lisp syntax rfc: (cond (EXPR => (lambda (X) ...))) Thien-Thi Nguyen
2011-01-02 21:57 ` Fren Zeee
2011-01-02 22:00 ` Fwd: " Fren Zeee
2011-01-02 22:52 ` Harald Hanche-Olsen
2011-01-04 16:41 ` Thien-Thi Nguyen
2011-01-04 17:56 ` Harald Hanche-Olsen
2011-01-04 18:39 ` Thien-Thi Nguyen
2011-01-03 2:19 ` Stefan Monnier
2011-01-04 17:00 ` Thien-Thi Nguyen
2011-01-03 16:15 ` Richard Stallman
2011-01-04 18:12 ` Thien-Thi Nguyen
2011-01-05 1:55 ` Stephen J. Turnbull
2011-01-05 3:21 ` Thien-Thi Nguyen
2011-01-05 4:16 ` Stephen J. Turnbull [this message]
2011-01-05 5:15 ` Miles Bader
2011-01-05 21:29 ` Stefan Monnier
2011-01-05 22:40 ` Harald Hanche-Olsen
2011-01-06 0:10 ` Stefan Monnier
2011-01-06 8:24 ` Helmut Eller
2011-01-07 3:49 ` Stefan Monnier
2011-01-06 18:43 ` Richard Stallman
2011-01-05 23:36 ` Richard Stallman
2011-01-11 17:20 ` Andy Wingo
2011-01-05 5:17 ` Miles Bader
-- strict thread matches above, loose matches on Subject: below --
2011-01-03 5:37 MON KEY
2011-01-04 17:20 ` Thien-Thi Nguyen
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