Issue #20: fix compass points parsing; refactor.

test/test_direction.py

@@ -0,0 +1,22 @@
+"""
+Test direction processing.
+
+Author: Sergey Vartanov (me@enzet.ru).
+"""
+import numpy as np
+
+from roentgen.direction import parse_vector
+
+
+def test_compass_points_1():
+    assert np.allclose(parse_vector("N"), np.array([0, -1]))
+
+
+def test_compass_points_2():
+    root: np.float64 = -np.sqrt(2) / 2
+    assert np.allclose(parse_vector("NW"), np.array([root, root]))
+
+
+def test_compass_points_3():
+    assert np.allclose(
+        parse_vector("SSW"), np.array([-0.38268343, 0.92387953]))