On 11-01-13 3:09 AM, Taras Zakharko wrote:
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:
The "(" function is not a function call operator. It's essentially a
no-op. I believe its only purpose is to help in deparsing, so that
things like (x + y) would deparse in the same way as entered.
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
You can use this syntax by defining a function `x<-` <- function(...) {}
and it could be an S3 method, but it is a completely separate object from x.
Duncan Murdoch
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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