/// <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)
/// </summary>
/// <param name="node"></param>
/// <param name="enum_children"></param>
/// <param name="enter_node"></param>
/// <returns></returns>
public static IEnumerable <WalkEvent <T> > Walk <T>(T node, Traversal.EnumerateChildren <T> enum_children, EnterNode <T> enter_node)
{
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 = new WalkEvent <T>(cur_item.Node, WalkEventType.Enter);
yield return(walkevent);
cur_item.Entered = true;
stack.Push(cur_item);
if (enter_node(cur_item.Node))
{
foreach (var child in Traversal.efficient_reverse(enum_children(cur_item.Node)))
{
stack.Push(new WalkState <T>(child));
}
}
}
else
{
var walkevent = new WalkEvent <T>(cur_item.Node, WalkEventType.Exit);
yield return(walkevent);
}
}
}
public static IEnumerable <WalkEvent <T> > Walk <T>(T node, Traversal.EnumerateChildren <T> enum_children)
{
return(Walk(node, enum_children, n => true));
}
