Region Calculus
ZPL’s region operators induce a “region calculus”
Let a dense r-dimensional region be speicifed by its upper and lower limit pairs: <l1,u1>,<l2,u2>... <lr,ur>
When d = (d1, d2 , ..., dr) and R = <l1,u1>,<l2,u2>... <lr,ur>, then
R at d = <l1+d1,u1+d1> <l2+d2,u2+d2 >...<lr+dr,ur+dr>
???<ui+1,ui+di> if di > 0
<li’,ui’> = ?? <li,ui> if di = 0
???<l1+di,li-1> if di < 0
(A more general formulation handles ZPL’s more general regions)