Dynamic Dictionary Data Type? 2005-06-02 - By Thomas Lumley
On Thu, 2 Jun 2005, hadley wickham wrote:
>> An environment is a hash table, and copying occurs only on modification,
>> when any language would have to copy in this context.
>
> Yes, I'm aware that copying only occurs on modification. However, it
> was my understanding that
>
> a <- list(a =1)
> a$b <- 4
>
> would create a new copy of a, whereas in Java say
>
It depends, but I was talking about *environments*, not lists, and
a<-new.env()
assign("b",4,a)
assign("c", 42, a)
etc
wouldn't copy anything. Bill Venables had an article about environments
for caching previously computed results in an early issue of R News.
-thomas
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