GNU bug report logs - #4290
23.1; (elisp)Anonymous Functions - unclear about #'

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: "Drew Adams" <drew.adams <at> oracle.com>
To: <bug-gnu-emacs <at> gnu.org>
Subject: 23.1; (elisp)Anonymous Functions - unclear about #'
Date: Sat, 29 Aug 2009 14:07:31 -0700

This Info node is unclear. It combines pre-Emacs 22 text that
explicitly says that lambda forms are *not* byte-compiled unless you
use `#'' or `function', with this statement that says that they are:
 
  Nowadays it is possible to omit `function' entirely, like this:
     (defun double-property (symbol prop)
       (change-property symbol prop (lambda (x) (* 2 x))))
  This is because `lambda' itself implies `function'.
 
What should be said is something like this:
 
"Starting with Emacs 22, a lambda form is byte-compiled when it is used
as a function, regardless of whether it is preceded by `function' or
`#''.  With Emacs versions prior to 22, you must explicitly use `#''
or `function' if you want the form to be byte-compiled."
 
This means rewording or replacing the paragraph that says that unless
you use `function' a lambda form won't be byte-compiled. The example
and its accompanying text need to be clarified.
 

In GNU Emacs 23.1.1 (i386-mingw-nt5.1.2600)
 of 2009-07-29 on SOFT-MJASON
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (4.4)'
 

Message #10 received at 4290 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Chong Yidong <cyd <at> stupidchicken.com>
To: "Drew Adams" <drew.adams <at> oracle.com>
Cc: emacs-devel <at> gnu.org, 4290 <at> debbugs.gnu.org
Subject: Re: 23.1; (elisp)Anonymous Functions - unclear about #'
Date: Fri, 11 Sep 2009 22:02:09 -0400

> This Info node is unclear. It combines pre-Emacs 22 text that
> explicitly says that lambda forms are *not* byte-compiled unless you
> use `#'' or `function', with this statement that says that they are:

>   Nowadays it is possible to omit `function' entirely, like this:
>      (defun double-property (symbol prop)
>        (change-property symbol prop (lambda (x) (* 2 x))))
>   This is because `lambda' itself implies `function'.

Thanks for spotting this.

Hmm---is `function' still useful for anything?

Message #15 received at 4290 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: "Drew Adams" <drew.adams <at> oracle.com>
To: "'Chong Yidong'" <cyd <at> stupidchicken.com>
Cc: <emacs-devel <at> gnu.org>, <4290 <at> debbugs.gnu.org>
Subject: RE: 23.1; (elisp)Anonymous Functions - unclear about #'
Date: Fri, 11 Sep 2009 23:13:03 -0700

> > This Info node is unclear. It combines pre-Emacs 22 text that
> > explicitly says that lambda forms are *not* byte-compiled unless you
> > use `#'' or `function', with this statement that says that they are:
> 
> >   Nowadays it is possible to omit `function' entirely, like this:
> >      (defun double-property (symbol prop)
> >        (change-property symbol prop (lambda (x) (* 2 x))))
> >   This is because `lambda' itself implies `function'.
> 
> Thanks for spotting this.
> 
> Hmm---is `function' still useful for anything?

At the very least it is needed for comptability with older Emacs versions. It
needs to be tolerated, at least.

Message #20 received at 4290 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Chong Yidong <cyd <at> stupidchicken.com>
Cc: "Drew Adams" <drew.adams <at> oracle.com>, 4290 <at> debbugs.gnu.org,
        emacs-devel <at> gnu.org
Subject: Re: 23.1; (elisp)Anonymous Functions - unclear about #'
Date: Sat, 12 Sep 2009 15:41:15 -0400

> Thanks for spotting this.
> Hmm---is `function' still useful for anything?

Well, it's just as useful as ever.  I.e. it's useless when you consider
that its implementation is the same as `quote', but it's otherwise
indispensable (e.g. look at the implementation of the `lambda' macro in
subr.el).


        Stefan

Message #25 received at 4290-done <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Chong Yidong <cyd <at> stupidchicken.com>
To: "Drew Adams" <drew.adams <at> oracle.com>
Cc: 4290-done <at> debbugs.gnu.org
Subject: Re: 23.1; (elisp)Anonymous Functions - unclear about #'
Date: Sat, 12 Sep 2009 21:49:48 -0400

I have clarified the text.  Thanks for the bug report.

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