V2.9.0 changes [Sec=Unclassified]

Well...

My performance problems were in the pass-by-value semantics of R.

I have just changed my classes to inherit from .environment and then moved data members from S4 slots to the .xData objects as Martin suggested.

Note that the R.oo and proto packages already use environments for
their storage. e.g.

library(proto)
p <- proto(a = 1, incr = function(.) .$a <- .$a + 1)
class(p) # c("proto", "environment")

p$a # 1
p$incr()
p$a # 2

p$ls() #  c("a", "incr")
ls(p) # same