Run Non-Interactive Function with Prefix

Run Non-Interactive Function with Prefix

[Kenneth Jacker]

If I want to execute a function that supports a "prefix" argument
interactively, I enter something like:

     C-u M-x foobar

How can I do the same thing but *non*-interactively?

This will just run 'foobar',

     (foobar)

But how to request it to be run with a prefix arg?


Something simple I am sure, but I can't seem to find a way to do it.

Thanks for your ideas!
-- 
Prof Kenneth H Jacker       khj@cs.appstate.edu
Computer Science Dept       www.cs.appstate.edu/~khj
Appalachian State Univ
Boone, NC  28608  USA        

Re: Run Non-Interactive Function with Prefix

[Lennart Borgman]

Kenneth Jacker wrote:

>If I want to execute a function that supports a "prefix" argument
>interactively, I enter something like:
>
>     C-u M-x foobar
>
>How can I do the same thing but *non*-interactively?
>
>This will just run 'foobar',
>
>     (foobar)
>
>But how to request it to be run with a prefix arg?
>  
>
Do you mean (foobar ARG), perhaps (foobar t) or (foobar 1)?

Re: Run Non-Interactive Function with Prefix

[Kenneth Jacker]

  lb> Do you mean (foobar ARG), perhaps (foobar t) or (foobar 1)?

No.  The function 'foobar' might or might not require an ARG.  


What I want to do is specify a *prefix* before invoking 'foobar'.
Note that this is independent of whether the function has a required
argument or not.

I specify this interactively with "C-u", but how to do it *non*-interactively?

  -Kenneth

Re: Run Non-Interactive Function with Prefix

[Lennart Borgman]

Kenneth Jacker wrote:

>  lb> Do you mean (foobar ARG), perhaps (foobar t) or (foobar 1)?
>
>No.  The function 'foobar' might or might not require an ARG.  
>
>
>What I want to do is specify a *prefix* before invoking 'foobar'.
>Note that this is independent of whether the function has a required
>argument or not.
>
>I specify this interactively with "C-u", but how to do it *non*-interactively?
>
>  -Kenneth
>  
>
I am not sure I understand (or rather "I am sure I do not understand" ;-)

In the CVS version of Emacs there is information about this Info:

   (elisp) Prefix Command Arguments

Maybe that can help you?

Re: Run Non-Interactive Function with Prefix

[Pascal Bourguignon]

Kenneth Jacker <khj@be.cs.appstate.edu> writes:

>   lb> Do you mean (foobar ARG), perhaps (foobar t) or (foobar 1)?
>
> No.  The function 'foobar' might or might not require an ARG.  
>
>
> What I want to do is specify a *prefix* before invoking 'foobar'.
> Note that this is independent of whether the function has a required
> argument or not.
>
> I specify this interactively with "C-u", but how to do it *non*-interactively?

But really, prefixes are awkward.  We cope with them for interactive
commands, but for functions it is silly to try to use them.

For functions, the best is to pass arguments.  If you have optional
arguments, then declare them optional: 

(defun foo (mandatory-arg-1 mandatory-arg-2 
            &optional optional-arg-1 optional-arg-2)
     ...)

When you call interactively a function, you must type:
M-: (foo "arg1" 2 :optional-value-1) RET


In some cases you can use global variables:
(defvar *parameter-for-foo* :default-value)

(defun foo ()
    ...
    *parameter-for-foo* 
    ...)

When you call interactively a function, you must type:

M-: (let ((*parameter-for-foo* :my-value)) (foo)) RET

or:

M-: (setf *parameter-for-foo* :new-value) RET
M-: (foo) RET


If you insist on prefix, then write a command! Just insert
(interactive) at the right place.

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/
Grace personified,
I leap into the window.
I meant to do that.

Re: Run Non-Interactive Function with Prefix

[Anselm Helbig]

hi, 

for interactive functions, the prefix argument becomes part of the
argument list, if it is referenced in the interactive declaration. you
can read more about it here:

	(info "(elisp)Prefix Command Arguments")

so if you want to call an interactive function from a program, you
have to figure out which argument corresponds to the prefix
argument. in the worst case scenario, you have to parse the
interactive declaration yourself. but since there already is code that
does just that, chances are you don't have to. 

regards, 

anselm

Re: Run Non-Interactive Function with Prefix

[Kevin Rodgers]

Kenneth Jacker wrote:
 > If I want to execute a function that supports a "prefix" argument
 > interactively, I enter something like:
 >
 >      C-u M-x foobar
 >
 > How can I do the same thing but *non*-interactively?
 >
 > This will just run 'foobar',
 >
 >      (foobar)
 >
 > But how to request it to be run with a prefix arg?

(let ((prefix-arg '(4))) ; C-u
   (call-interactively 'foobar))

-- 
Kevin Rodgers

Re: Run Non-Interactive Function with Prefix

[Kenneth Jacker]

  kr> (let ((prefix-arg '(4))) ; C-u
  kr>    (call-interactively 'foobar))

Just what I needed!

Thanks for your and everyone else's comments ...

  -Kenneth