Refactoring: move a nested function to the module level; add tests for it
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Alexey Zakharenkov
Alexey Zakharenkov
parent
a9c32e3c12
commit
e53683655d
2 changed files with 171 additions and 12 deletions
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@ -130,19 +130,21 @@ def is_near(p1, p2):
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)
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def project_on_line(p, line):
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def project_on_segment(p, p1, p2):
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dp = (p2[0] - p1[0], p2[1] - p1[1])
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d2 = dp[0] * dp[0] + dp[1] * dp[1]
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if d2 < 1e-14:
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return None
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# u is the position of projection of p point on line p1p2
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# regarding point p1 and (p2-p1) direction vector
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u = ((p[0] - p1[0]) * dp[0] + (p[1] - p1[1]) * dp[1]) / d2
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if not 0 <= u <= 1:
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return None
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return u
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def project_on_segment(p, p1, p2):
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"""Given three points, return u - the position of projection of
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point p onto segment p1p2 regarding point p1 and (p2-p1) direction vector
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"""
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dp = (p2[0] - p1[0], p2[1] - p1[1])
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d2 = dp[0] * dp[0] + dp[1] * dp[1]
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if d2 < 1e-14:
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return None
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u = ((p[0] - p1[0]) * dp[0] + (p[1] - p1[1]) * dp[1]) / d2
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if not 0 <= u <= 1:
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return None
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return u
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def project_on_line(p, line):
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result = {
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# In the first approximation, position on rails is the index of the
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# closest vertex of line to the point p. Fractional value means that
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157
tests/test_projection.py
Normal file
157
tests/test_projection.py
Normal file
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@ -0,0 +1,157 @@
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import collections
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import itertools
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import unittest
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from subway_structure import project_on_segment
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class TestProjection(unittest.TestCase):
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"""Test subway_structure.project_on_segment function"""
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PRECISION = 10 # decimal places in assertAlmostEqual
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SHIFT = 1e-6 # Small distance between projected point and segment endpoint
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def _test_projection_in_bulk(self, points, segments, answers):
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"""Test 'project_on_segment' function for array of points and array
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of parallel segments projections on which are equal.
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"""
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for point, ans in zip(points, answers):
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for seg in segments:
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for segment, answer in zip(
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(seg, seg[::-1]), # What if invert the segment?
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(ans, None if ans is None else 1 - ans),
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):
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u = project_on_segment(point, segment[0], segment[1])
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if answer is None:
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self.assertIsNone(
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u,
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f"Project of point {point} onto segment {segment} "
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f"should be None, but {u} returned",
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)
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else:
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self.assertAlmostEqual(
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u,
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answer,
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self.PRECISION,
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f"Wrong projection of point {point} onto segment "
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f"{segment}: {u} returned, {answer} expected",
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)
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def test_projection_on_horizontal_segments(self):
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points = [
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(-2, 0),
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(-1 - self.SHIFT, 0),
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(-1, 0),
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(-1 + self.SHIFT, 0),
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(-0.5, 0),
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(0, 0),
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(0.5, 0),
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(1 - self.SHIFT, 0),
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(1, 0),
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(1 + self.SHIFT, 0),
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(2, 0),
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]
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horizontal_segments = [
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((-1, -1), (1, -1)),
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((-1, 0), (1, 0)),
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((-1, 1), (1, 1)),
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]
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answers = [
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None,
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None,
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0,
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self.SHIFT / 2,
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0.25,
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0.5,
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0.75,
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1 - self.SHIFT / 2,
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1,
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None,
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None,
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]
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self._test_projection_in_bulk(points, horizontal_segments, answers)
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def test_projection_on_vertical_segments(self):
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points = [
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(0, -2),
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(0, -1 - self.SHIFT),
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(0, -1),
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(0, -1 + self.SHIFT),
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(0, -0.5),
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(0, 0),
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(0, 0.5),
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(0, 1 - self.SHIFT),
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(0, 1),
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(0, 1 + self.SHIFT),
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(0, 2),
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]
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vertical_segments = [
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((-1, -1), (-1, 1)),
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((0, -1), (0, 1)),
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((1, -1), (1, 1)),
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]
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answers = [
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None,
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None,
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0,
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self.SHIFT / 2,
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0.25,
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0.5,
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0.75,
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1 - self.SHIFT / 2,
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1,
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None,
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None,
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]
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self._test_projection_in_bulk(points, vertical_segments, answers)
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def test_projection_on_inclined_segment(self):
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points = [
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(-2, -2),
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(-1, -1),
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(-0.5, -0.5),
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(0, 0),
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(0.5, 0.5),
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(1, 1),
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(2, 2),
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]
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segments = [
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((-2, 0), (0, 2)),
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((-1, -1), (1, 1)),
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((0, -2), (2, 0)),
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]
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answers = [None, 0, 0.25, 0.5, 0.75, 1, None]
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self._test_projection_in_bulk(points, segments, answers)
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def test_projection_with_different_collections(self):
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"""The tested function should accept points as any consecutive
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container with index operator.
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"""
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types = (tuple, list, collections.deque,)
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point = (0, 0.5)
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segment_end1 = (0, 0)
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segment_end2 = (1, 0)
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for p_type, s1_type, s2_type in itertools.product(types, types, types):
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p = p_type(point)
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s1 = s1_type(segment_end1)
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s2 = s2_type(segment_end2)
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project_on_segment(p, s1, s2)
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def test_projection_on_degenerate_segment(self):
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coords = [-1, 0, 1]
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points = [(x, y) for x, y in itertools.product(coords, coords)]
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segments = [
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((0, 0), (0, 0)),
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((0, 0), (0, 1e-8)),
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]
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answers = [None] * len(points)
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self._test_projection_in_bulk(points, segments, answers)
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