A Newbie question :-) Is it possible to fill TreeView (tree is naturally recursive) with a nonrecursive/iterative thinking paradigm? Are there some good examples regarding this matter in the Internet?

I post this question in FPC mailing list because my question actually about filling a "tree" in general.

Thanks in advance.

i probably shouldn't open my mouth, as i don't quite understand the question... however FRED from the game Freespace let you design missions using a treeview.

It involved following a tree like
|- when 'Enemy Cargo ship' is 'attacked'
| \- then 'enemy support ships' do 'jump in'
|- when 'Enemy Cargo ship' is 'destroyed'
| \- then 'mission successful'
|- etc...

or do you mean the other way around where the thinking paradigm fills in the treeview?

- V

Vannus wrote

i probably shouldn't open my mouth, as i don't quite understand the question... however FRED from the game Freespace let you design missions using a

treeview.

Just to make my question clear, for example, I can fill a TreeView control with particular Registry keys by enumerating registry keys recursively and put them in the TreeView control; then for performance reason, I attempt to use a nonrecursive/iterative approach to enumerate registry keys, but how can I fill the TreeView since a "tree" is naturally recursive? Is recursion is the only way to achive it?

Hello FPC-Pascal,

Wednesday, September 1, 2010, 11:20:57 PM, you wrote:

BA> Just to make my question clear, for example, I can fill a TreeView control with BA> particular Registry keys by enumerating registry keys recursively and put them BA> in the TreeView control; then for performance reason, I attempt to use a BA> nonrecursive/iterative approach to enumerate registry keys, but how can I fill BA> the TreeView since a "tree" is naturally recursive? Is recursion is the only way BA> to achive it?

You must know at which node a new node must be inserted, but you can write something like (pseudo code):

procedure FillConditional(var ParentNode: TNode);
var
  j: integer;
  l: TList;
  n: TNode;
begin
  l:=TList.Create;
  n:=nil;
  for j:=0 to xxxx do begin //xxx is some kind of condition
    n:=TNode.Create;
    n.position:=j;
    Tree.AddNode(ParentNode,n);
    if j=10 then begin
      l.add(n); //Remember the node at position 10
    end;
  end;
  for j:=0 to n.Count-1 do begin
    n:=l.Items[j];
    FillConditional(n);
  end;
  l.free;
end;

It is recursive, but first you add all sibliings and them you add each new brach linearly.

José Mejuto wrote

You must know at which node a new node must be inserted...

If your input data contains a string which always identifies the parent node then you can map the string -> "parent node" and find it later for adding a child node.

Pseudo code again:

var
  ParentNode, Node: TNode;
  Map: TStringHashMap;
  ParentId, Id: string;
...
  //  get data from somewhere
  ParentId := ...
  Id := ...
  ParentNode := Map[ParentId];
  // This should make Node a root node if ParentNode = nil.
  Node := Tree.AddNode(ParentNode, Id);  // Pseudo syntax.
  Map[Id] := Node;   // Use as parent for following nodes.

If you don't have such ID then you must use recursion.

Juha

When reading from registry and populating a treeview, a recursive function is the least of your worries regarding "performance" (or memory, if you're careful).

-Flávio

Thanks José and Juha, now I see the light. :-)

Flávio Etrusco wrote

When reading from registry and populating a treeview, a recursive function is the least of your worries regarding "performance" (or memory, if you're careful).

I'm a crash-phobia :-). Stack sizes are different among the OS platforms. A superdeep recursion will trigger a stack overflow exception.