* bug#15538: 24.3; Incorrect Expansion of Nested Backquote
@ 2013-10-06 11:23 白井 彰
2013-10-08 4:30 ` Stefan Monnier
2013-10-28 22:47 ` Nathan Trapuzzano
0 siblings, 2 replies; 3+ messages in thread
From: 白井 彰 @ 2013-10-06 11:23 UTC (permalink / raw)
To: 15538; +Cc: okshirai
The expansion of nested backquote like
``(,,@q)
or
``(,@,@q)
is incorrect.
Please see the following results.
; The followings are from CLtL2 Appendix C. Backquote
(require 'cl-lib)
cl-lib
(setq q '(r s))
(r s)
(defun r (x) (cl-reduce #'* x))
r
(setq r '(3 5))
(3 5)
(setq s '(4 6))
(4 6)
``(,,q)
(\` ((\, (r s))))
(24) ; Correct
``(,@,q)
(\` ((\,@ (r s))))
24 ; Correct
``(,,@q)
(\` ((\, r s)))
((3 5)) ; Incorrect: This should be
((3 5) (4 6))
``(,@,@q)
(\` ((\,@ r s)))
(3 5) ; Incorrect: This should be (3
5 4 6)
(setq x '(b c))
(b c)
(setq y '(a b))
(a b)
(setq p '(cl-union x y))
(cl-union x y)
(setq q '((cl-union x y) (list 'sqrt 9)))
((cl-union x y) (list (quote sqrt) 9))
(setq r '(cl-union x y))
(cl-union x y)
(setq s '((cl-union x y)))
((cl-union x y))
``(foo ,,p)
(\` (foo (\, (cl-union x y))))
(foo (a b c)) ; Correct
``(foo ,,@q)
(\` (foo (\, (cl-union x y) (list (quote sqrt) 9))))
(foo (a b c)) ; Incorrect: This should be
(foo (a b c) (sqrt 9))
``(foo ,',r)
(\` (foo (\, (quote (cl-union x y)))))
(foo (cl-union x y)) ; Correct
``(foo ,',@s)
(\` (foo (\, (quote (cl-union x y)))))
(foo (cl-union x y)) ; Correct
``(foo ,@,p)
(\` (foo (\,@ (cl-union x y))))
(foo a b c) ; Correct
``(foo ,@,@q)
(\` (foo (\,@ (cl-union x y) (list (quote sqrt) 9))))
(foo a b c) ; Incorrect: This should be
(foo a b c sqrt 9)
``(foo ,@',r)
(\` (foo (\,@ (quote (cl-union x y)))))
(foo cl-union x y) ; Correct
``(foo ,@',@s)
(\` (foo (\,@ (quote (cl-union x y)))))
(foo cl-union x y) ; Correct
In GNU Emacs 24.3.1 (i386-apple-darwin9.8.0, NS apple-appkit-949.54)
of 2013-04-30 on mini2.local
Windowing system distributor `Apple', version 10.3.949
Configured using:
`configure '--with-ns' '--without-x''
Important settings:
value of $LANG: ja_JP.ujis
locale-coding-system: japanese-iso-8bit-unix
default enable-multibyte-characters: t
Major mode: Lisp Interaction
Minor modes in effect:
tooltip-mode: t
mouse-wheel-mode: t
tool-bar-mode: t
menu-bar-mode: t
file-name-shadow-mode: t
global-font-lock-mode: t
font-lock-mode: t
blink-cursor-mode: t
auto-composition-mode: t
auto-encryption-mode: t
auto-compression-mode: t
line-number-mode: t
transient-mark-mode: t
Recent input:
<escape> x r e p o r t - e m a c s - b u g <return>
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Load-path shadows:
None found.
Features:
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mm-util mail-prsvr mail-utils time-date japan-util tooltip ediff-hook
vc-hooks lisp-float-type mwheel ns-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode register page
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base64 format env code-pages mule custom widget hashtable-print-readable
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^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#15538: 24.3; Incorrect Expansion of Nested Backquote
2013-10-06 11:23 bug#15538: 24.3; Incorrect Expansion of Nested Backquote 白井 彰
@ 2013-10-08 4:30 ` Stefan Monnier
2013-10-28 22:47 ` Nathan Trapuzzano
1 sibling, 0 replies; 3+ messages in thread
From: Stefan Monnier @ 2013-10-08 4:30 UTC (permalink / raw)
To: 白井 彰; +Cc: 15538
> ``(,,@q)
> (\` ((\, r s)))
> ((3 5)) ; Incorrect: This should be ((3 5)
> (4 6))
Indeed, it's incorrect, but I think the intention of the current code is
to consider the above expression as invalid, so the error is to return
a value at step 2 (ignoring the second argument `s' to the unquote)
instead of signalling an error.
If you really want that result, you can do
``(,@(list ,@q))
> ``(,@,@q)
And here, you'd have to use
``(,@(append ,@q))
I installed a patch into trunk which catches the above problems and
signals an error if/when encountering such situations.
Thank you,
Stefan
^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#15538: 24.3; Incorrect Expansion of Nested Backquote
2013-10-06 11:23 bug#15538: 24.3; Incorrect Expansion of Nested Backquote 白井 彰
2013-10-08 4:30 ` Stefan Monnier
@ 2013-10-28 22:47 ` Nathan Trapuzzano
1 sibling, 0 replies; 3+ messages in thread
From: Nathan Trapuzzano @ 2013-10-28 22:47 UTC (permalink / raw)
To: 15538
Stefan,
Is there any reason why double unquote/unquote-splicing can't work in
Emacs? A comment in your commit seems to suggest it's doable, so may I
ask why you decided not to implement it? I suspect many macro-writing
macros would be much more readable if they could be written as they
often are in Common Lisp.
Nathan
^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-10-06 11:23 bug#15538: 24.3; Incorrect Expansion of Nested Backquote 白井 彰
2013-10-08 4:30 ` Stefan Monnier
2013-10-28 22:47 ` Nathan Trapuzzano
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