On 08 Feb 2005 21:49:47 +0100, Peter Dalgaard <[EMAIL PROTECTED]> wrote :
>Duncan Murdoch <[EMAIL PROTECTED]> writes: > >> Looking in envir.c, I see this: >> >> /* env is now R_NilValue, the base environment */ >> >> which doesn't give me much hope, but maybe there's a trick.... >> >> If not, would it be reasonable to install a magic "EmptyEnv" to use as >> a parent in this sort of situation? >> > >I'm fairly sure the answer is "nope". > >It's been annoying me for years, for language aesthetic reasons >mostly, but also with some consideration of cases like yours, and I've >been on the brink of implementing a version where the base environment >was a true environment. Apart from the usual issue of "round tuits", >I was held back by the fact that one has to consider at least two things: > >(a) efficiency. Is it expensive no longer to have the base functions >bound directly to their symbol? (My gut feeling is that with suitable >hashing and cacheing, the penalty is minimal.) > >(b) you can *only* use get and simple variable retrieval in a non-base >environment with a NULL parent (eval(x <- 1, envir=foo) would give >'couldn't find function "<-"' or so). This could cause some confusion. (b) means that the default should stay the way it is, but I think there should be a way to set up a truly empty environment. We have a fair number of cases where envir=NULL is used, so it would be safest to make it a different value -- even if NULL is the obvious value for an empty environment. Duncan Murdoch ______________________________________________ R-devel@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
