static vector<Box> boxes (Grob *me, Grob *left);
static Skyline conditional_skyline (Grob *, Grob *);
static Grob *extremal_break_aligned_grob (Grob *, Direction, Interval *);
static vector<Box> boxes (Grob *me, Grob *left);
static Skyline conditional_skyline (Grob *, Grob *);
static Grob *extremal_break_aligned_grob (Grob *, Direction, Interval *);