Refer to List of Arguments in Emacs Lisp Function

Refer to List of Arguments in Emacs Lisp Function

[Alexander Shukaev]

Hello,

I can't find whether there is a possibility to refer to the whole list of
arguments of a function in Emacs Lisp. For example:

(defun move (x y z)
  (apply do-move (args))

What I mean by (args) primitive here is a list (x y z). This use case
illustrates usefulness of such a primitive, i.e. forwarding of arguments to
another internal call without a need to rewrite them by hand. (length
(args)) might be useful in some cases too. Is there anything like that in
Emacs Lisp already?

Re: Refer to List of Arguments in Emacs Lisp Function

[Marcin Borkowski]

On 2014-11-13, at 09:02, Alexander Shukaev wrote:

> Hello,
>
> I can't find whether there is a possibility to refer to the whole list of
> arguments of a function in Emacs Lisp. For example:
>
> (defun move (x y z)
>   (apply do-move (args))
>
> What I mean by (args) primitive here is a list (x y z). This use case
> illustrates usefulness of such a primitive, i.e. forwarding of arguments to
> another internal call without a need to rewrite them by hand. (length
> (args)) might be useful in some cases too. Is there anything like that in
> Emacs Lisp already?

(defun move (&rest args)
  (apply #'do-move args))

Note that (apply do-move (args)) would not work: first, you have to
quote do-move, second, (args) would try to call a function `args'.

Hth,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Adam Mickiewicz University

Re: Refer to List of Arguments in Emacs Lisp Function

[Barry Margolin]

In article <mailman.13556.1415895434.1147.help-gnu-emacs@gnu.org>,
 Marcin Borkowski <mbork@wmi.amu.edu.pl> wrote:

> On 2014-11-13, at 09:02, Alexander Shukaev wrote:
> 
> > Hello,
> >
> > I can't find whether there is a possibility to refer to the whole list of
> > arguments of a function in Emacs Lisp. For example:
> >
> > (defun move (x y z)
> >   (apply do-move (args))
> >
> > What I mean by (args) primitive here is a list (x y z). This use case
> > illustrates usefulness of such a primitive, i.e. forwarding of arguments to
> > another internal call without a need to rewrite them by hand. (length
> > (args)) might be useful in some cases too. Is there anything like that in
> > Emacs Lisp already?
> 
> (defun move (&rest args)
>   (apply #'do-move args))
> 
> Note that (apply do-move (args)) would not work: first, you have to
> quote do-move, second, (args) would try to call a function `args'.

You don't have to quote do-move if it's a variable, e.g. in a context 
like:

(let ((do-move (if something #'move1 #'move2)))
  (apply do-move (args)))

And I think he was actually asking if there's a function that returns 
all the arguments, which you would calls as (args).

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Re: Refer to List of Arguments in Emacs Lisp Function

[Joost Kremers]

Alexander Shukaev wrote:
> (defun move (x y z)
>   (apply do-move (args))

(defun move (&rest args)
  (apply #'do-move args)))

HTH

-- 
Joost Kremers                                   joostkremers@fastmail.fm
Selbst in die Unterwelt dringt durch Spalten Licht
EN:SiS(9)

Re: Refer to List of Arguments in Emacs Lisp Function

[Alexander Shukaev]

>
> (defun move (&rest args)
>   (apply #'do-move args)))
>

I'm aware of that, but that's not what I'm looking for... I'm interested in
required arguments in the first place.

Re: Refer to List of Arguments in Emacs Lisp Function

[Andreas Röhler]

On 13.11.2014 09:35, Alexander Shukaev wrote:
>>
>> (defun move (&rest args)
>>    (apply #'do-move args)))
>>
>
> I'm aware of that, but that's not what I'm looking for... I'm interested in
> required arguments in the first place.
>

What about that way:

(cadr (symbol-function 'MY-FUNCTION))

Re: Refer to List of Arguments in Emacs Lisp Function

[Nicolas Richard]

Andreas Röhler <andreas.roehler@easy-emacs.de> writes:
> What about that way:
>
> (cadr (symbol-function 'MY-FUNCTION))

I guess this will bomb in lexbind context, no ?

-- 
Nicolas Richard

Re: Refer to List of Arguments in Emacs Lisp Function

[Barry Margolin]

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In article <mailman.13561.1415897958.1147.help-gnu-emacs@gnu.org>,
 Andreas Röhler <andreas.roehler@easy-emacs.de> wrote:

> On 13.11.2014 09:35, Alexander Shukaev wrote:
> >>
> >> (defun move (&rest args)
> >>    (apply #'do-move args)))
> >>
> >
> > I'm aware of that, but that's not what I'm looking for... I'm interested in
> > required arguments in the first place.
> >
> 
> What about that way:
> 
> (cadr (symbol-function 'MY-FUNCTION))

That will return the names of the arguments, not the list of actual 
arguments in a call.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Re: Refer to List of Arguments in Emacs Lisp Function

[Stefan Monnier]

> That will return the names of the arguments, not the list of actual 
       ^^^^
       may

It may also signal an error.


        Stefan

Re: Refer to List of Arguments in Emacs Lisp Function

[Alexander Shukaev]

It seems to me that this feature is relatively easy to implement by
modifying the `defun' macro. Would anyone be interested to see this in
future release of Emacs?

Re: Refer to List of Arguments in Emacs Lisp Function

[Barry Margolin]

In article <mailman.13526.1415865742.1147.help-gnu-emacs@gnu.org>,
 Alexander Shukaev <haroogan@gmail.com> wrote:

> Hello,
> 
> I can't find whether there is a possibility to refer to the whole list of
> arguments of a function in Emacs Lisp. For example:
> 
> (defun move (x y z)
>   (apply do-move (args))
> 
> What I mean by (args) primitive here is a list (x y z). This use case
> illustrates usefulness of such a primitive, i.e. forwarding of arguments to
> another internal call without a need to rewrite them by hand. (length
> (args)) might be useful in some cases too. Is there anything like that in
> Emacs Lisp already?

I don't think there's any built-in way to get a list of the arguments 
that were named separately in the argument list. Emacs Lisp's argument 
processing is very similar to Common Lisp's, and it doesn't have a way 
to do it, either. So you have to refer to the named arguments themselves:

(defun move (x y z)
  (apply do-move (list x y z)))

(defun move (x y z)
  (funcall do-move x y z))

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Re: Refer to List of Arguments in Emacs Lisp Function

[Ted Zlatanov]

On Thu, 13 Nov 2014 09:02:14 +0100 Alexander Shukaev <haroogan@gmail.com> wrote: 

AS> I can't find whether there is a possibility to refer to the whole list of
AS> arguments of a function in Emacs Lisp. For example:

AS> (defun move (x y z)
AS>   (apply do-move (args))

AS> What I mean by (args) primitive here is a list (x y z). This use case
AS> illustrates usefulness of such a primitive, i.e. forwarding of arguments to
AS> another internal call without a need to rewrite them by hand.

I think `apply-partially' and function aliasing are more typical
solution for this use case in today's Emacs. Macros also help, depending
on the situation. Not to say your need is not valid, but it's definitely
not common.

AS> (length (args)) might be useful in some cases too. Is there anything
AS> like that in Emacs Lisp already?

Sorry... I'm not aware of such a thing.

Ted