Re: [CFCDev] recursive functions

[Doug Keen]

You may want to check out this article:
http://www.sitepoint.com/article.php/1105
It's a really good explanation of using a "modified preorder tree 
traversal" algorithm for storing and navigating trees (which may make 
your "pruning" problem much easier!)  The article is specifically in the 
context of storing trees/hierarchical structures in a relational 
database, but the translation of these database structures into CFCs 
should be relatively straightforward.

A fair warning... it definitely took me a couple times reading through 
the article to really grasp what the author was talking about!  Though 
there are definitely some tradeoffs to consider with the modified 
preorder tree traversal algorithm, it seems like a pretty solid solution 
for many different situations and is something to consider.

-Doug (CFCDev Newbie)

Nando wrote:

Do a walk of the tree, maintaining a list of nodeIDs (pageID or something)
that grows and shrinks as you walk.
   

Ummm ... sounds like i SHOULD know what this means but i don't. Not familar
with the term 'walk' in programming speak. How does the list grow and shrink
When you find your node (the current
 

page), abort the walk.  The start a new walk that will actually generate
your pruned tree, and use that list that you build (which will contain the
path to the target node) to determine what branches you need to
process and
which branches you can skip.
   

I probably don't understand this, again, because of the 'walk' term. Do you
have a few minutes to explain a little more sometime?
[In the back of the class with arm raised ...]

Nando

You'll probably want to prepend a
 

NULL to the
front, so that the 'parent' of the topmost node is represented in
your list.
Typically, you want to display the children of all the nodes in the list,
but nothing else.
You can use a loop for both walks, and I'd definitely recommend it for the
first walk, as a loop is a lot easier to break (CFBREAK) than a recursive
function.
Cheers,
barneyb
   

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Nando
Sent: Monday, December 01, 2003 3:25 PM
To: [EMAIL PROTECTED]
Subject: RE: [CFCDev] recursive functions
I'm caching the results of a few recursive function in an
object that create
a tree structure of the site nav and a linked breadcrumb
trail for each page
in the site. So the performance hit is only taken once in a
great while. I
DO have to agree with Sean that the code is much more
elegant, and the depth
of the tree is unlimited, something i didn't see how to do
with loops, (but
might now if i really thought about it.)
The next challenge is how to "prune" the siteMap tree to
display only the
navigation tree needed for a particular page - hopefully
that's easy, but i
haven't looked into it yet.
     

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Sean A Corfield
Sent: Monday, December 01, 2003 11:40 PM
To: [EMAIL PROTECTED]
Subject: Re: [CFCDev] recursive functions
On Dec 1, 2003, at 1:47 PM, Patrick Branley wrote:
       

This is a very good point. Anything that can be done with
         

recursion
     

can also
be done using a loop.
         

Sometimes implementing an algorithm with a loop makes for horrendous
code whereas recursive code can be elegant and simple - consider
algorithms for processing tree-structured data!
       

Does anybody know if there is a performance increase ? I
         

would assume
     

there
isnt.
         

It depends. Recursion relies on function calls which can be
       

expensive
     

(creating a stack frame, pushing variables etc). If the algorithm is
sufficiently complex, the extra work you have to do to
       

manage 'context'
     

for a loop may exceed the function call overhead.

Sean A Corfield -- http://www.corfield.org/blog/

"If you're not annoying somebody, you're not really alive."
-- Margaret Atwood
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