/// <summary>
// Walks a Node in a depth-first/pre-order manner without recursion.
// It returns a series of "events" that indicate one of three things:
// - whether it has enters into a node
// - whether it has exited from a node (i.e. it is finished with that container and its children)
// - caller can control which children get entered via the enum_children method
/// </summary>
public static IEnumerable <WalkEvent <T> > Walk <T>(T node, EnumerateChildren <T> enum_children)
{
var stack = new Stack <WalkState <T> >();
// put the first item on the stack
stack.Push(new WalkState <T>(node));
// As long as something is on the stack, we are not done
while (stack.Count > 0)
{
var cur_item = stack.Pop();
if (cur_item.Entered == false)
{
var walkevent = WalkEvent <T> .CreateEnterEvent(cur_item.Node);
yield return(walkevent);
cur_item.Entered = true;
stack.Push(cur_item);
foreach (var child in TreeOps.efficient_reverse(enum_children(cur_item.Node)))
{
stack.Push(new WalkState <T>(child));
}
}
else
{
var walkevent = WalkEvent <T> .CreateExitEvent(cur_item.Node);
yield return(walkevent);
}
}
}
public static IList <TDest> CopyTree <TSrc, TDest>(
TSrc src_root_node,
System.Func <TSrc, IEnumerable <TSrc> > enum_src_children,
System.Func <TSrc, TDest> create_dest_node,
System.Action <TDest, TDest> add_dest_child)
{
var stack = new Stack <TDest>();
var dest_nodes = new List <TDest>();
var walkevents = TreeOps.Walk <TSrc>(src_root_node, input_node => enum_src_children(input_node));
foreach (var ev in walkevents)
{
if (ev.HasEnteredNode)
{
var new_dst_node = create_dest_node(ev.Node);
if (stack.Count > 0)
{
// if there is node on the stack, then that node is the current node's parent
var parent = stack.Peek();
add_dest_child(parent, new_dst_node);
}
else
{
// if there is nothing on the stack this is node without a parent (a root node)
}
stack.Push(new_dst_node);
dest_nodes.Add(new_dst_node);
}
else if (ev.HasExitedNode)
{
stack.Pop();
}
}
return(dest_nodes);
}
public static IEnumerable <T> PreOrder <T>(T root, EnumerateChildren <T> enum_children)
{
return(TreeOps.Walk(root, enum_children).Where(ev => ev.HasEnteredNode).Select(ev => ev.Node));
}