C-u prefix input (e.g., C-x f / set-fill-column)

C-u prefix input (e.g., C-x f / set-fill-column)

[David Reitter]

The documentation for `fill-column' reads:

 > Interactively, you can set the buffer local value using C-x f.

When you do C-x f, you get an error message "set-fill-column requires  
an explicit argument".

(The documentation for `set-fill-column' is okay.)

I would propose two changes:

1. The documentation should be

"Interactively, you can set the buffer local value using C-u <VALUE>  
C-x f."


2a. When users forget to give an argument with C-u, the error message  
should be

"set-fill-column requires an explicit argument with prefix C-u  
<ARGUMENT>"

or something like that.
Or, better:

2b. Instead of displaying the above error message, the user should be  
queried interactively for the argument, just like most interactive  
functions do it. In other words, use (interactive "N") in `set-fill- 
column' instead of "p".


FWIW, interactive "p" is used 213 times, but in most situations, the  
prefix seems to be optional, i.e. the change to "N" wouldn't be  
justified.

Re: C-u prefix input (e.g., C-x f / set-fill-column)

[Ulrich Mueller]

>>>>> On Fri, 19 Oct 2007, David Reitter wrote:

> 2a. When users forget to give an argument with C-u, the error message  
> should be

> "set-fill-column requires an explicit argument with prefix C-u  
> <ARGUMENT>"

> or something like that.
> Or, better:

> 2b. Instead of displaying the above error message, the user should be  
> queried interactively for the argument, just like most interactive  
> functions do it. In other words, use (interactive "N") in `set-fill- 
> column' instead of "p".

Wouldn't (current-column) be a reasonable default if no explicit
argument was given?

Ulrich

Re: C-u prefix input (e.g., C-x f / set-fill-column)

[Tassilo Horn]

Ulrich Mueller <ulm@gentoo.org> writes:

Hi Ulrich,

>> 2a. When users forget to give an argument with C-u, the error message
>> should be
>
>> "set-fill-column requires an explicit argument with prefix C-u
>> <ARGUMENT>"
>
>> or something like that.
>> Or, better:
>
>> 2b. Instead of displaying the above error message, the user should be
>> queried interactively for the argument, just like most interactive
>> functions do it. In other words, use (interactive "N") in `set-fill-
>> column' instead of "p".
>
> Wouldn't (current-column) be a reasonable default if no explicit
> argument was given?

I would object here.  (current-column) is a good default for
`set-goal-column', but for `set-fill-column' I'd prefer if it queries
the user if no prefix arg was given.

Bye,
Tassilo

Re: C-u prefix input (e.g., C-x f / set-fill-column)

[Ulrich Mueller]

>>>>> On Fri, 19 Oct 2007, Tassilo Horn wrote:

>> Wouldn't (current-column) be a reasonable default if no explicit
>> argument was given?

> I would object here.  (current-column) is a good default for
> `set-goal-column', but for `set-fill-column' I'd prefer if it queries
> the user if no prefix arg was given.

Hi Tassilo,

next time I shall read the source code _before_ posting. ;-)
Function set-fill-column contains the following comment:
;; Disallow missing argument; it's probably a typo for C-x C-f.

So the point is that plain "C-x f" should produce an error because it
is too similar to "C-x C-f". No default, and no further query.

Ulrich

Re: C-u prefix input (e.g., C-x f / set-fill-column)

[David Reitter]

On 19 Oct 2007, at 18:30, Ulrich Mueller wrote:

> So the point is that plain "C-x f" should produce an error because it
> is too similar to "C-x C-f". No default, and no further query.

I think a further query would be appropriate. It is non-destructive,  
easy to abort, and conveys the same message via the prompt.

(It's too late to choose a different binding!) 

Re: C-u prefix input (e.g., C-x f / set-fill-column)

[Juri Linkov]

>> So the point is that plain "C-x f" should produce an error because it
>> is too similar to "C-x C-f". No default, and no further query.
>
> I think a further query would be appropriate. It is non-destructive,  easy
> to abort, and conveys the same message via the prompt.

Maybe this is for newbies who don't know how to abort this prompt
with C-g?

> (It's too late to choose a different binding!)

Late or not, a good and easy to remember key binding would be `C-x M-q'.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: C-u prefix input (e.g., C-x f / set-fill-column)

[Richard Stallman]

I'd rather not make a change in this.