R help - Feb 2021 - Is it Possible to Create S4 Function Objects?

Hi Abby,

Something along the line of:

   setClass("S4Function",
     contains="function",
     representation(name="character", more_stuff="ANY")
   )

seems to do what you want:

   f <- new("S4Function", function(a) a^2, name="square")

   # 'f' is both an S4 object and a function:
   is.object(f)
   # [1] TRUE
   is.function(f)
   # [1] TRUE

   f at name
   # [1] "square"
   f(11)
   # [1] 121

Hope this helps,

H.

On 2/12/21 1:53 PM, Abby Spurdle (/??bi/) wrote:
> Dear All,
> 
> I was wondering if it's possible to create S4 function objects?
> (Or S4 closures, if you prefer).
> 
> i.e.
> An R object, that is both an S4 object, and a function.
> 
> This would allow one to write:
> 
>> f <- constructor4.functionobj ()
>> f ()
>> f at slot.of.f
> 
> I've searched for this, but I can't find any examples.
> 
> If it's possible, then that leads to the question of if/how the body
> of f() could directly access the value of the slot?
> 
>> f <- function ()
>>     this at slot.of.f
> 
> I should note that the more common approach of storing values in a
> function's environment, doesn't work well for top-level objects.
> This approach is dependent on immutability of the function's data, and
> I'm reluctant to create such constraints.
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
-- 
Herv? Pag?s

Bioconductor Core Team
hpages.on.github at gmail.com

Oh wow.
Post of the year!
Where's the like button?

Note, I was able to rewrite it without the deprecated args.
(Don't want one of those CRAN emails, in 12 months from now, saying
please change XXXX).

I'll have to come back to this later, to see if I can get the body of
f() to access the slot


On Mon, Feb 22, 2021 at 11:36 AM Herv? Pag?s <hpages.on.github at
gmail.com> wrote:
>
> Hi Abby,
>
> Something along the line of:
>
>    setClass("S4Function",
>      contains="function",
>      representation(name="character", more_stuff="ANY")
>    )
>
> seems to do what you want:
>
>    f <- new("S4Function", function(a) a^2,
name="square")
>
>    # 'f' is both an S4 object and a function:
>    is.object(f)
>    # [1] TRUE
>    is.function(f)
>    # [1] TRUE
>
>    f at name
>    # [1] "square"
>    f(11)
>    # [1] 121
>
> Hope this helps,
>
> H.