(tests): adds checks for accessors of mat3 type

tests/python/mat3_test.py

@@ -3,7 +3,7 @@
 import numpy as np
 import math3d as m3d
 
-from typing import Type, Union, List, cast
+from typing import Type, Union, cast
 
 Matrix3Cls = Type[Union[m3d.Matrix3f, m3d.Matrix3d]]
 Vector3Cls = Type[Union[m3d.Vector3f, m3d.Vector3d]]
@@ -16,6 +16,10 @@ def mat3_all_close(mat: Matrix3, mat_np: np.ndarray, epsilon: float = 1e-5) -> b
     return np.allclose(cast(np.ndarray, mat), mat_np, atol=epsilon)
 
 
+def vec3_all_close(vec: Vector3, vec_np: np.ndarray, epsilon: float = 1e-5) -> bool:
+    return np.allclose(cast(np.ndarray, vec), vec_np, atol=epsilon)
+
+
 @pytest.mark.parametrize(
     "Mat3, Vec3, FloatType",
     [
@@ -56,7 +60,36 @@ def test_numpy_array_constructor(
     ) -> None:
         mat = Mat3(
             np.array(
-                [[1.0, 2.0, 3.0], [4.0, 5.0, 6.0], [7.0, 8.0, 9.0]], dtype=FloatType
+                [[1.0, 2.0, 3.0], [4.0, 5.0, 6.0], [7.0, 8.0, 9.0]],
+                dtype=FloatType,
             )
         )
         assert mat3_all_close(mat, np.arange(1, 10).reshape(3, 3).astype(FloatType))
+
+
+@pytest.mark.parametrize(
+    "Mat3, Vec3, FloatType",
+    [
+        (m3d.Matrix3f, m3d.Vector3f, np.float32),
+        (m3d.Matrix3d, m3d.Vector3d, np.float64),
+    ],
+)
+def test_mat3_accessors(Mat3, Vec3, FloatType) -> None:
+    mat = Mat3(
+        np.array([[1.0, 2.0, 3.0], [4.0, 5.0, 6.0], [7.0, 8.0, 9.0]], dtype=FloatType)
+    )
+
+    # __getitem__ by using a single entry should return the requested column
+    col0, col1, col2 = mat[0], mat[1], mat[2]
+    assert type(col0) == Vec3 and type(col1) == Vec3 and type(col2) == Vec3
+    assert vec3_all_close(col0, np.array([1.0, 4.0, 7.0], dtype=FloatType))
+    assert vec3_all_close(col1, np.array([2.0, 5.0, 8.0], dtype=FloatType))
+    assert vec3_all_close(col2, np.array([3.0, 6.0, 9.0], dtype=FloatType))
+
+    # __getitem__ by using a tuple
+    assert mat[0, 0] == 1.0 and mat[0, 1] == 2.0 and mat[0, 2] == 3.0
+    assert mat[1, 0] == 4.0 and mat[1, 1] == 5.0 and mat[1, 2] == 6.0
+    assert mat[2, 0] == 7.0 and mat[2, 1] == 8.0 and mat[2, 2] == 9.0
+
+    # __getitem__ by using a slice
+    # TODO(wilbert): implement __getitem__ to retrieve a view of the vector