RE: AS 2.0 optimising.. 2004-03-16 - By Metanet Software
Back
hi,
i just wanted to mention something: i agree with the "usage" qualifier, i
guess i was specifically referring to looking up a single value.
two comments:
(1)
using the object as a hashlist to avoid having to loop through a list
searching for a match has nothing to do with object-vs-array, it's simply
using the abstract data type most suitable for the job.
(2)
"I am guessing that they are using a dictionary internally, a hashtable
where values
are indexed as strings [String name, Object value]."
i'm almost positive that arrays are implemented as double-linked-lists
internally, which accoutns for the O(n) lookups. a hashtable would really
such for things like shifting/etc...
anyway, i just wanted to be a bit more specific in case the info helps
anyone; a couple months ago i ran some tests, i could probably find the code
if anyone case, but basically i was comparing arrays to objects in two
cases; i used integer "keys" for the object, i.e
list = new Object();
list[0] = "jimmy";
-looking up a single element at a known index:
objects took constant time, arrays took linear time (based on the length of
the array).
so, objects are MUCH faster if you have larage lists and you frequently
lookup a single value (for instance, any kind of look-up-table would be
faster if implemented as an object instead of an array)
-iterating over all elements (using a for..in loop)
this took approx. the same amount of time for both array and objects
even if you wanted to only iterate over a subsection of the list, as long as
you use integers as the hash-keys, you can use objects instead of arrays..
so, what am i missing? because it seems to me that arrays are sort of
useless...
raigan
__ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ __
MSN Premium includes powerful parental controls and get 2 months FREE*
http://join.msn.com/?pgmarket=en-ca&page=byoa/prem&xAPID=1994&DI=1034&SU=http:/
/hotmail.com/enca&HL=Market_MSNIS_Taglines
=-- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- --
Supported by Fig Leaf Software
=-- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- --
Be sure to check the archives and the wiki:
http://chattyfig.figleaf.com/
=-- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- --
http://chattyfig.figleaf.com/cgi-bin/ezmlm-cgi?1:mss:107117
=-- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- --
To unsubscribe send a blank e-mail to:
Normal Mode: flashcoders-unsubscribe@(protected)
Digest Mode: flashcoders-digest-unsubscrive@(protected)
|
|
