[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

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

Subject: Re: Cheaper to prepend or append an item to a sequence?
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Tue, 22 Feb 2011 22:07:37 +0000
Re:  Cheaper to prepend or append an item to a sequence
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?

When one list A is a sublist of another list B, A does not need separate storage - it can be implemented by means of pointers to the first and last items from B that are to be included in A. Therefore if A is not already a sublist of another list, you can create B by making a longer list and making A a sublist of the new list. Saxon does this using arrays rather than linked lists, but the same principle would work either way.

Michael Kay

Current Thread


Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!

Buy Stylus Studio Now

Download The World's Best XML IDE!

Accelerate XML development with our award-winning XML IDE - Download a free trial today!

Don't miss another message! Subscribe to this list today.
First Name
Last Name
Subscribe in XML format
RSS 2.0
Atom 0.3
Site Map | Privacy Policy | Terms of Use | Trademarks
Free Stylus Studio XML Training:
W3C Member
Stylus Studio® and DataDirect XQuery ™are products from DataDirect Technologies, is a registered trademark of Progress Software Corporation, in the U.S. and other countries. © 2004-2013 All Rights Reserved.