Re: [R] Is it Possible to Create S4 Function Objects?

[/əˈbi/]

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 ).

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 Hervé Pagès  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@name
># [1] "square"
>f(11)
># [1] 121
>
> Hope this helps,
>
> H.

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Re: [R] Is it Possible to Create S4 Function Objects?

[/əˈbi/]

It appears that my previous post may lack clarity.

So, I've created three examples of mathematical function objects.
(One) using a standard closure with lexical scoping, (two) using S3
with an attribute and (three) using S4 with a slot.
Each example constructs the function object via a constructor (of some
form), plots it, then prints the attribute/etc.
However, the third example with S4 is incomplete.

Any suggestions welcome.

begin code

plotf <- function (f)
{   x <- seq (-1, 1,, 200)
plot (x, f (x), type="l")
}

#standard closure, with lexical scoping
quad.lex <- function (p = c (0, 0, 1) )
{   function (x)
p [1] + p [2] * x + p [3] * x^2
}

#s3-based function object, with attribute
quad.s3 <- function (p = c (0, 0, 1) )
{   f <- function (x)
{   this <- sys.function ()
p <- attr (this, "p")
p [1] + p [2] * x + p [3] * x^2
}
attr (f, "p") <- p
f
}

#s4-based function object, with slot
setClass ("Quad.S4", slots = list (p="numeric") )
Quad.S4 <- function (p = c (0, 0, 1) )
{   #?
}

f.lex <- quad.lex ()
plotf (f.lex)
environment (f.lex)$p

f.s3 <- quad.s3 ()
plotf (f.s3)
attr (f.s3, "p")

f.s4 <- Quad.S4 ()
#plotf (f.s4)
#f.s4@p


On Sat, Feb 13, 2021 at 10:53 AM Abby Spurdle (/əˈbi/)
 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...@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 ()
> >t...@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.

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[R] Is it Possible to Create S4 Function Objects?

[/əˈbi/]

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...@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 ()
>t...@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@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.