subtract in region%

Sets the region to the subtraction of itself minus the given region. In other words, a point is removed from the region if it is included in the given region. (The given region may contain points that are not in the current region; such points are ignored.)

For post-script-dc% output, region subtraction is not reliable, especially for subtractions involving arc regions or more than two regions.

This region's DC and given region's DC must be the same.

• (send a-region subtract rgn) -> void
     rgn : region% object