key-value mapping in C inside R?

On Dec 30, 2010, at 7:50 AM, Matteo Bertini wrote:

I'm testing some modifications in arima.c.
I've noticed that a big internal array of double (rbar) is usually sparse and I'd like to add an option to store it as key-value mapping.

Is there a library function or some other approach already used inside the R core for key-value mappings?

environment created with hash=TRUE, e.g.:
e = new.env(TRUE, emptyenv())
e[["foo"]] = "bar"

You can even set "size" with the expected size if you know it in advance.