>>>>> "Robin" == Robin Hankin <[EMAIL PROTECTED]>
>>>>> on Thu, 7 Sep 2006 12:18:51 +0100 writes:
Robin> Thank you for this. Minimal self-contained code included below.
Robin> It is slightly modified from the original because brob objects have
two
Robin> slots, both of which are needed by c().
Robin> [
Robin> A "brob" obect is represents a real number with two slots: "x"
holds
Robin> its natural
Robin> logarithm; slot "positive" is Boolean, indicating whether the number
Robin> is positive.
Robin> I want this because I need to manipulate numbers up to ~1e20000.
Robin> The hard bit is addition: log(exp(x) + exp(y)) == x +
log1p(exp(y-x))
Robin> ]
I know and I really like your idea.
However....
Robin> It seemed to make sense to coerce non-brob arguments to brobs,
Robin> then make cPair() use cPairOfBrobs() [with coerced arguments] in
Robin> three of the cases, and c() for the fourth with signature c("ANY",
Robin> "ANY").
Robin> Now below, JC states that "cWithMethods() _replaces_ the ordinary c
Robin> (), it's not
Robin> just a method for it". Does this imply that one cannot set up an R
Robin> package
Robin> so that the following code:
Robin> x <- as.brob(1:10)
Robin> x1 <- c(1,x)
Robin> x2 <- c(x,1)
Robin> works as expected?
No. There's no way {which does not break much other R code} currently.
More than two days ago,
I had told you (and the R-devel readers) that you should look at
help(cbind2) {and said why}.
If you *really* look at it, and then
think about or better study the code underlying
the methods:::bind_activation(TRUE)
kludge,
you will shudder (and run :-) and probably understand that a
similar kludge for c() is not appropriate.
Robin> Or is there some workaround that would enable me to do this?
well, yes: As John Chambers has tried to say, you have to teach
your users to use cWithPairs() or c2() or myC() or c.() or any
reasonable name, but not c().
Martin
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