> So, if I have understood correctly, having
> 
>    $sequence[last()]
> 
> (and somehow more than one reference to $sequence)
> will guarantee that any further access to the items of $sequence will
> be performed in constant time?

No guarantees: but yes, that's what I would expect to happen.
> 
> Cant this be pre-computed automatically by the XSLT processor?
> Something like computing a function with @memo-function="yes", but
> done by the XSLT processor?

I'm not clear what you mean.

Michael Kay
http://www.saxonica.com/