Re: Cheaper to prepend or append an item to a sequence

On Tue, Feb 22, 2011 at 8:32 AM, Michael Kay <mike@xxxxxxxxxxxx> wrote:

> Even with a forward-chained list, you can implement append without copying
> if you choose, at least for the first append operation to a given list
> (which 9 times out of 10 will be the only append operation).

How is that?  If I have X=[1,2,3] ; Y=X ; Z=Y++[4]

How can Z append Y without copying it first?  You of course cannot
modify Y in FP at all (which you know), much less w/o changing X.

I'm confused.