// parallel version of the same higher-order function
public void ParMapTree(TreeMapperDelegate f)
{
var i = 0;
var tasks = new Task[3];
var t1 = Task.Factory.StartNew(() => this.Value = f(this.Value));
tasks[i++] = t1;
if (Left != null)
{
var t2 = Task.Factory.StartNew(() => this.Left.ParMapTree(f));
tasks[i++] = t2;
}
if (Right != null)
{
var t3 = Task.Factory.StartNew(() => this.Right.ParMapTree(f));
tasks[i++] = t3;
}
Task.WaitAll(tasks);
}
// higher-order functions over trees
public void MapTree(TreeMapperDelegate f)
{
Value = f(Value);
Left?.MapTree(f);
Right?.MapTree(f);
}