dg3c: ensure that arguments to up are exactly 3d (#313)

Adds tuple unpacking from inputs for d3ga up function, so that it throws a ValueError if a list of the wrong length is passed.

clifford/dg3c.py

@@ -38,7 +38,8 @@ def up_cga1(pnt_vector):
     Take a vector and embed it as a point in the first
     copy of cga
     """
-    euc_point = pnt_vector[0]*e1 + pnt_vector[1]*e2 + pnt_vector[2]*e3
+    x, y, z = pnt_vector
+    euc_point = x*e1 + y*e2 + z*e3
     return euc_point + 0.5*(euc_point|euc_point)*einf1 + eo1
 
 
@@ -54,7 +55,8 @@ def up_cga2(pnt_vector):
     Take a vector and embed it as a point in the second
     copy of cga
     """
-    euc_point = pnt_vector[0]*e6 + pnt_vector[1]*e7 + pnt_vector[2]*e8
+    x, y, z = pnt_vector
+    euc_point = x*e6 + y*e7 + z*e8
     return euc_point + 0.5*euc_point**2*einf2 + eo2
 
 

clifford/test/test_dg3c.py

@@ -1,4 +1,5 @@
 import unittest
+import pytest
 import numpy as np
 from ..dg3c import *
 
@@ -40,6 +41,10 @@ def test_up_down(self):
             res = down(100*pnt)
             np.testing.assert_allclose(res, pnt_vector)
 
+        # Assert an error is raised if the point is not 3d
+        with pytest.raises(ValueError):
+            up([1, 2, 3, 4])
+
     def test_up_down_cga1(self):
         """
         Test that we can map points up and down from cga1
@@ -51,6 +56,10 @@ def test_up_down_cga1(self):
             res = down_cga1(100*pnt)
             np.testing.assert_allclose(res, pnt_vector)
 
+        # Assert an error is raised if the point is not 3d
+        with pytest.raises(ValueError):
+            up_cga1([1, 2, 3, 4])
+
 
 class GeometricPrimitiveTests(unittest.TestCase):
     def test_reciprocality(self):