bug#4290: 23.1; (elisp)Anonymous Functions - unclear about #'

bug#4290: 23.1; (elisp)Anonymous Functions - unclear about #'

[Drew Adams]

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)'
 

Re: 23.1; (elisp)Anonymous Functions - unclear about #'

[Chong Yidong]

> 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?

bug#4290: 23.1; (elisp)Anonymous Functions - unclear about #'

[Chong Yidong]

> 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?

bug#4290: 23.1; (elisp)Anonymous Functions - unclear about #'

[Drew Adams]

> > 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.

RE: 23.1; (elisp)Anonymous Functions - unclear about #'

[Drew Adams]

> > 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.

bug#4290: 23.1; (elisp)Anonymous Functions - unclear about #'

[Stefan Monnier]

> 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

Re: 23.1; (elisp)Anonymous Functions - unclear about #'

[Stefan Monnier]

> 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