>># 
>># Copyright 1990, 1991 by the Massachusetts Institute of Technology and
>># UniSoft Group Limited.
>># 
>># Permission to use, copy, modify, distribute, and sell this software and
>># its documentation for any purpose is hereby granted without fee,
>># provided that the above copyright notice appear in all copies and that
>># both that copyright notice and this permission notice appear in
>># supporting documentation, and that the names of MIT and UniSoft not be
>># used in advertising or publicity pertaining to distribution of the
>># software without specific, written prior permission.  MIT and UniSoft
>># make no representations about the suitability of this software for any
>># purpose.  It is provided "as is" without express or implied warranty.
>># 
>># $XConsortium: unnrgn.m,v 1.6 92/06/11 17:43:45 rws Exp $
>># 
>>#
>>TITLE XUnionRegion CH10
>>ASSERTION A XUnionRegion-1
A call to XUnionRegion computes the union of the regions
sra and srb and places the result in the region dr_return.
>>STRATEGY
Create regions R1 R2 R3 using XCreateRegion.
Set regions R1 and R2 to right-angled triangles joined along the hypotenuse using XPolygonRegion.
Set R3 to the rectangle formed by joining the triangles using XUnionRectWithRegion.
Obtain the union of R1 and R2 using XUnionRegion.
Verify that union is the same as R3 using XEqualRegion.

Create a region using XCreateRegion.
Set the region to an overlapping set of 3x3 rectangular regions using XUnionRegion.
Verify that the result is the correct rectangular region using XEqualRegion.
