private ImTreeMapIntToObj AddOrUpdate(int key, object value, bool updateOnly, UpdateValue update)
{
return(Height == 0 ? // tree is empty
(updateOnly ? this : new ImTreeMapIntToObj(key, value, Empty, Empty))
: (key == Key ? // actual update
new ImTreeMapIntToObj(key, update == null ? value : update(Value, value), Left, Right)
: (key < Key // try update on left or right sub-tree
? With(Left.AddOrUpdate(key, value, updateOnly, update), Right)
: With(Left, Right.AddOrUpdate(key, value, updateOnly, update))).KeepBalanced()));
}
