-#if defined (__GNUG__) && ! defined (__STRICT_ANSI__)
- left = h.left >? left;
- right = h.right <?right;
-#else
- left = max (h.left, left);
- right = min (h.right, right);
-#endif
+ at (LEFT) = min (h.at (LEFT), at (LEFT));
+ at (RIGHT) = max (h.at (RIGHT), at (RIGHT));