- s1.left = MAX(s1.left, s2.left), s1.right = MAX(s1.right, s2.right), \
- s1.top = MAX(s1.top, s2.top), s1.bottom = MAX(s1.bottom, s2.bottom)
+ (s1).left = MAX((s1).left, (s2).left), \
+ (s1).right = MAX((s1).right, (s2).right), \
+ (s1).top = MAX((s1).top, (s2).top), \
+ (s1).bottom = MAX((s1).bottom, (s2).bottom)