code: function parentise(tree, h)
  {
  	if (h === tree.height)
  	{
  		return tree;
  	}
  
  	return {
  		ctor: '_Array',
  		height: h,
  		table: [parentise(tree, h - 1)],
  		lengths: [length(tree)]
  	};
  }
docs: Recursively creates a tree that contains the given tree.