/**
* Main program.
*
* @param array $args Command-line arguments.
* @return integer Zero on success; non-zero on failure.
*/
public static function main($args)
{
printf("BinaryTree main program.\n");
$status = 0;
$bt = new BinaryTree(box(4));
$bt->attachLeft(new BinaryTree(box(2)));
$bt->attachRight(new BinaryTree(box(6)));
AbstractTree::test($bt);
return $status;
}