There is no post above, so I guess something went wrong. But from an RSS feed, I found your original question.

"Hi

I have extended the DefaultTreeNode class and added my own customized index to each TreeNode as a field to the derived class.
Now I want to implement a corresponding method to search for the particular tree node based on its above defined unique index.
How to search for that tree node based upon my own index?

What I'm doing is that, first of all I'm trying to get the TreeModel out of the tree. Then trying to use the TreeModel.walk-nodes with the proc-type{TreeNode}:bool .
but I'm not able to implement it properly.

Any pointer or other apporoach?"

but I also notice this did show up in another thread, so this duplicate thread can be ignored.

Hi friedger

I was asking about how to make use of MyTreeNode::walk-nodes which has been derived form DefaultTreeNode and added an extra field for custom indexing.
And in the proc-type I want to compare my custom index to a passed index value...like...

{define-class public IndexTreeNode {inherits DefaultTreeNode}
field constant public node-index:int
{constructor public {default node-data:any = null, node-index:int}
set self.node-index = node-index
{construct-super node-data = node-data}
}

{method public {get-node-from-node-index nodeindex:int}:any
||Search for the node with the node-index and return

||First get the TreeModel for this sub tree
let tm:#TreeModel = self.tree-model
{if tm == null then return null}

let tn:#IndexTreeNode = {tm.walk-nodes
{proc {t:IndexTreeNode}:bool
{return t.node-index == nodeindex}
}
}
{return tn}
}
}

The above code is just for sample and I want to compare for my node-index inside the proc-type of TreeModel.walk-nodes.

hope you got my problem.

BTY, how you are able to post the code in a text area with proper alignment. I was trying with Rich Text posting but all my white spaces are truncated.

Thank you. Even I had tried to, do that method inside the proc-type.

But I'm totally confused with the exception that I'm getting from begining that .....

 
 
 
NullDereferenceException: Attempt to use <b>null</b> where a non-<b>null</b> value is required at (0x081BE2C4). 
 
 
#0 IndexTreeNode.get-node-from-node-index (0x081be2c3+87) at file:///d:/Sample Apps/My Tree/indextreenode.scurl:??
#1 build-tree-model (0x041bdd45+465) at file:///d:/Sample Apps/My Tree/start.curl:??
#2 [evaluator <b>for</b> <unnamed>] (0x088c011e+34) at file:///d:/Sample Apps/My Tree/start.curl:??
#3 EvalTopLevelEnv.finish-and-run-aux (0x02116375+613)
#4 EvalTopLevelEnv.finish-and-run (0x021160e2+142)
#5 IncrementalEvaluatorFile.evaluate-next (0x029ce875+557)
#6 IncrementalEvaluator.evaluate-next (0x029ce5a7+65)
#7 Applet.load-next-aux (0x029ccd51+737)
#8 Applet.load-next (0x029cc8c4+156)
#9 [http://{proc} inside Applet.load-start|http://{proc} inside Applet.load-start] (0x029cc814+16)
#10 closure_raw_handler (0x0037efda+26)
#11 AlarmQueue.dispatch-alarms (0x02589061+289)
#12 EventQueue.dispatch-events (0x01be02bf+175)
#13 dispatch-events (0x01be01d1+53)
#14 event-loop (?) (0x01be0197+9)
#15 run-applet (0x023c56f8+136)
#16 ProcessRunnable.run-bound-proc (0x01bc834e+1238)
#17 ProcessRunnable.run (0x01bc7e72+10)
#18 curl-thread-really-really-call-run-in-runnable (0x01bc7e4c+18)
#19 curl-thread-really-call-run-in-runnable (0x01bc3d59+233) 
 
 

And the following code is in my start.curl file

 
 
 
let mytreenode:IndexTreeNode = {IndexTreeNode node-data = "My Tree", 0}
{mytreenode.append {IndexTreeNode node-data = "ABC", 1}}
{mytreenode.append {IndexTreeNode node-data = "XYZ", 2}}
 
 
let n:#IndexTreeNode = {mytreenode.get-node-from-node-index 1} || I want to get the node ABC here as its node-index is 1 
 
 

Thank you very much Mr friedger .

You can not believe, that pair of curly brackets for return statement had already griended my brain since morning and I were unable to find that silly mistake.

Thank you again.

The problem is that syntaxes in Curl are first-class objects, so 'return' without curly braces is a reference to the 'CompilerSyntax' object that implements the 'return' syntax. There is not much that users can do with these objects, but you can create an alias using 'def', which can be useful when writing macros that extend existing syntaxes or just to provide shorthand for verbose syntaxes. For example, you can write:

   def uninitialized = uninitialized-value-for-type
 
   let s:String = {uninitialized String}

Obviously, this idiom should be used sparingly since it could create a lot of confusion.

So regarding your case, the only error the compiler would be able to produce would be that the value 'return' is not used. We have sometimes talked about adding a compile-time error or warning for unused values, but have not done so to date.