Add Rectangle:
Rectangle:
PROC [context: Context, lowerLeft, upperRight:
VEC, zip: Zip ←
NIL] ~ {
Rectangle is arbitrarily oriented with respect to the axes.
This can take advantage of the Bresenham stuff, as suggested by Blob Wyvill, by:
using the transpose of the first line to get the perpendicular,
and using an offset to get the parallel line.