[R] Method dispatch for function call operator?

[Taras Zakharko]

Dear R gurus,

 I am trying to create a nicer API interface for some R modules I have
written. Here, I heavily rely on S3 method dispatch mechanics and
makeActiveBinding()  function

 I have discovered that I apparently can't dispatch on function call
operator (). While .Primitive("(") exists, which leads me to believe that
things like x(...) are internally translated to .Primitive("(")(x, ...), I
can't seem to do something like:

x <- integer()
class(x) <- "testclass"
"(.testclass" <- function(o, x, y) print(paste(x, y))
x(1, 2)

Similar code does work for other operators like "[".

A workaround I have discovered is to make x a function from the beginning
and then extend the functionality by via S3 methods. Unfortunately, it does
not allow me to do something I'd really like to - use syntax like this:

x(...) <- y

For this, I'd need to dispatch on something like

"(<-.testclass" <- function(x, arglist, value) 

Currently, I am using the index operator for this (i.e. x[...] <- y) - it
works nicely, but I'd prefer the () syntax, if possible. 

 Does anyone know a way to do this?

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