If you change 'area' to an environment, you may be able to get
something close to what you want.
For example:
setClass("Square",
representation(
length='numeric',
width='numeric',
area='environment'
),
prototype(
length=0,
width=0,
area=new.env()
)
)
setGeneric("area", function(x) standardGeneric("area"))
setMethod("area", "Square",
function(x){
if (length(ls(x...@area)) == 0){
message("Computing")
assign("area", x...@width * x...@length, envi...@area)
}
message("Accessing")
get("area", envi...@area)
})
tmp <- new("Square", length=5, width=10)
area(tmp) ## This should show "computing" and "accessing"
area(tmp) ## the 2nd call should show 'accessing' only
b
On Oct 14, 2009, at 3:31 PM, Steve Lianoglou wrote:
Hi,
I was wondering if there was a way to store the results of a
computationally expensive "getter" call on an S4 object, so that it is
only calculated once for each object.
Trivial example: let's say I want to cache the "expensive" area
calculation of a square object.
setClass("Square",
representation(
length='numeric',
width='numeric',
area='numeric'
),
prototype(
length=0,
width=0,
area=-1
)
)
setGeneric("area", function(x) standardGeneric("area"))
setMethod("area", "Square",
function(x) {
if (x...@area == -1) {
x...@area <- x...@width * x...@height
}
x...@area
})
Now the first time I call ``area(my.square)`` it computes
``my.squ...@width * my.squ...@height``, but each subsequent call
returns `...@area`` since the area computation has already been calc'd
and set for this object.
Is this possible? I'm guessing the R pass by value semantics is going
to make this one difficult ... is there some S4 reference I missed
that has this type of info from?
Thanks,
-steve
--
Steve Lianoglou
Graduate Student: Computational Systems Biology
| Memorial Sloan-Kettering Cancer Center
| Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact
______________________________________________
R-help@r-project.org mailing list
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.
______________________________________________
R-help@r-project.org mailing list
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.
