Fix error message

[linpy.git] / examples / tesseract.py

diff --git a/examples/tesseract.py b/examples/tesseract.py
index 0a57188..d692e37 100755 (executable)
--- a/examples/tesseract.py
+++ b/examples/tesseract.py
@@ -1,23 +1,28 @@
 #!/usr/bin/env python3
 
-from linpy import *
+# In geometry, the tesseract is the four-dimensional analog of the cube; the
+# tesseract is to the cube as the cube is to the square. Just as the surface of
+# the cube consists of 6 square faces, the hypersurface of the tesseract
+# consists of 8 cubical cells.
+
+from linpy import Le, symbols
+
 
 x, y, z, t = symbols('x y z t')
 
-tesseract = \
-    Le(0, x) & Le(x, 1) & \
-    Le(0, y) & Le(y, 1) & \
-    Le(0, z) & Le(z, 1) & \
-    Le(0, t) & Le(t, 1)
+tesseract = Le(0, x, 1) & Le(0, y, 1) & Le(0, z, 1) & Le(0, t, 1)
+
 
 def faces(polyhedron):
     for points in polyhedron.faces():
         face = points[0].aspolyhedron()
-        face = face.union(*[point.aspolyhedron() for point in points[1:]])
-        face = face.aspolyhedron()
+        face = face.convex_union(*[point.aspolyhedron()
+                                   for point in points[1:]])
         yield face
 
-print('Faces of tesseract\n\n  {}\n\nare:\n'.format(tesseract))
-for face in faces(tesseract):
-    assert(len(face.vertices()) == 8)
-    print('  {}'.format(face))
+
+if __name__ == '__main__':
+    print('Faces of tesseract\n\n  {}\n\nare:\n'.format(tesseract))
+    for face in faces(tesseract):
+        assert(len(face.vertices()) == 8)
+        print('  {}'.format(face))