GNU bug report logs - #6893
evaluating `'#'(lambda (b) b)8 ; => 8 with `eval-last-sexp' "C-x C-e" in `emacs-lisp-mode'

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: MON KEY <monkey <at> sandpframing.com>
Subject: bug#6893: closed (Re: bug#6893: evaluating `'#'(lambda (b) b)8 ;
 => 8 with `eval-last-sexp' "C-x C-e" in `emacs-lisp-mode')
Date: Sat, 21 Aug 2010 22:46:03 +0000

[Message part 1 (text/plain, inline)]

Your bug report

#6893: evaluating `'#'(lambda (b) b)8 ; => 8 with `eval-last-sexp' "C-x C-e" in `emacs-lisp-mode'

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 6893 <at> debbugs.gnu.org.

-- 
6893: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=6893
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

[Message part 2 (message/rfc822, inline)]

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: MON KEY <monkey <at> sandpframing.com>
Subject: Re: bug#6893: evaluating `'#'(lambda (b) b)8 ;
	=> 8 with `eval-last-sexp' "C-x C-e" in `emacs-lisp-mode'
Date: Sun, 22 Aug 2010 00:40:17 +0200

> Interactive invocation of `eval-last-sexp' (e.g. "C-x C-e" ) in
> Emacs-lisp mode buffer for this form:

>  `'#'(lambda (b) b)8
>  ;=> 8

C-x C-e doesn't evaluate "the expression on the line" but "the last sexp
before point".
The "last-sexp" is just "8" (try C-M-b to see what it is), so whatever
other sexp you put before won't make any difference.


        Stefan

[Message part 3 (message/rfc822, inline)]

From: MON KEY <monkey <at> sandpframing.com>
To: bug-gnu-emacs <at> gnu.org
Subject: evaluating `'#'(lambda (b) b)8 ; => 8 with `eval-last-sexp' "C-x C-e"
	in `emacs-lisp-mode'
Date: Sat, 21 Aug 2010 17:55:03 -0400

Interactive invocation of `eval-last-sexp' (e.g. "C-x C-e" ) in
Emacs-lisp mode buffer for this form:

 `'#'(lambda (b) b)8
 ;=> 8

`eval-last-sexp' for this makes (some) sense:

 `'#'(lambda (b) b)
 ;=> (quote (function (lambda (b) b)))

And so, presumably the above is equivalent to:

 (eval '(list 'quote '(function (lambda (b) b))))
 ;=> (quote (function (lambda (b) b)))

But what is the equivalent form which would explain the results for
following:

 `'#'(lambda (b) b)8
 ;=> 8

Surely it isn't this:

 (funcall (eval (eval (eval '(list 'quote '(function (lambda (b) b)))))) 8)
 ;=> 8

If it is, then why is eval'ing the same `'#'(lambda (b) b)8 form with
`eval-expression' (e.g. "M-:") met with the message:

 "Trailing garbage following expression"

Likewise, giving `eval-expression' this form lands me in the debugger:

 (`'#'(lambda (b) b) 8)

 ;=> Debugger entered--Lisp error:
     (wrong-number-of-arguments #[(structure) "\301!A\207"
                                  [structure backquote-process] 2 1720176] 2)

Reproducable on 23.2 with emacs -Q

--
/s_P\

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