added attributes to Arc. created unittests

Author: chenkasirer

src/compas/geometry/primitives/arc.py

@@ -1,3 +1,6 @@
+import math
+
+from compas.geometry import close
 from compas.geometry.primitives import Frame
 from compas.geometry.primitives import Primitive
 
@@ -12,8 +15,24 @@ class Arc(Primitive):
     radius : float
         Radius of the arc's circle.
     end_angle : float
-        The angle in radians of the
-    end_angle :
+        The angle in radians of the end of this Arc.
+    start_angle :
+        The angle in radians of the start of this Arc.
+
+    Attributes
+    ----------
+    length : float
+        The length of the arc (radius * angle)
+    angle : float
+        The sweep angle in radians (between incrementing end angle and start angle).
+    domain : tuple(float, float)
+        A tuple containing the start and end angles of this arc, in radians.
+    center : :class:`~compas.geometry.Point`
+        The center point of the circle which coincides with this Arc.
+    circumference : float
+        The circumference of the circle which coincides with this Arc.
+    diameter : float
+        The diameter of the circle which coincides with this Arc.
 
     """
 
@@ -22,9 +41,12 @@ def __init__(self, frame=None, radius=None, end_angle=None, start_angle=None, **
 
         self._frame = frame
         self._radius = radius
-        self._start_angle = start_angle
+        self._start_angle = start_angle if start_angle is not None else 0.0
         self._end_angle = end_angle
 
+        if self._radius is not None and self._end_angle is not None:
+            self._verify()
+
     @property
     def data(self):
         return {"frame": self._frame.data, "radius": self._radius, "start": self._start_angle, "end": self._end_angle}
@@ -44,10 +66,65 @@ def frame(self):
     def radius(self):
         return self._radius
 
+    @property
+    def length(self):
+        return self.radius * self.angle
+
     @property
     def start_angle(self):
         return self._start_angle
 
     @property
     def end_angle(self):
         return self._end_angle
+
+    @property
+    def angle(self):
+        return self._end_angle - self._start_angle
+
+    @property
+    def domain(self):
+        return self._start_angle, self._end_angle
+
+    @property
+    def center(self):
+        return self.frame.point
+
+    @property
+    def circumference(self):
+        return 2.0 * math.pi * self.radius
+
+    @property
+    def diameter(self):
+        return 2.0 * self.radius
+
+    @property
+    def is_circle(self):
+        return close(abs(abs(self.angle) - 2.0 * math.pi), 0.0)
+
+    @classmethod
+    def from_circle(cls, circle, start_angle, end_angle):
+        """Creates an Arc from a circle and start and end angles.
+
+        Parameters
+        ----------
+        circle : :class:`~compas.geometry.Circle`
+            The center point and radius of this circle will be used to create an Arc.
+        start_angle : float
+            The start angle in radians.
+        end_angle : float
+            The end angle in radians.
+
+        Returns
+        -------
+        :class:`~compas.geometry.Arc`
+
+        """
+        frame = Frame.worldXY()
+        # TODO: take circle.frame once it has one
+        frame.point = circle.center.copy()
+        return cls(frame, circle.radius, end_angle, start_angle)
+
+    def _verify(self):
+        if self.angle < 0.0 or self.angle > 2.0 * math.pi:
+            raise ValueError("Sweep angle must satisfy 0 < angle < 2 * Pi. Currently:{}".format(self.angle))

tests/compas/geometry/test_arc.py

@@ -0,0 +1,62 @@
+import math
+import pytest
+
+from compas.geometry import Arc
+from compas.geometry import Frame
+from compas.geometry import Plane
+from compas.geometry import Circle
+from compas.geometry import close
+
+
+@pytest.fixture
+def frame():
+    return Frame([1.23, 0.44, -4.02], [1., 0., 0.], [0., 1., 0.])
+
+
+def test_create_arc(frame):
+    arc = Arc(frame, 0.2, 1.14)
+
+    assert close(arc.angle, 1.14)
+    assert close(arc.start_angle, 0.0)
+
+
+def test_create_arc_two_angles(frame):
+    arc = Arc(frame,radius=8, start_angle=1.44, end_angle=3.14)
+
+    assert close(arc.radius, 8.0)
+    assert close(arc.angle, 1.7)
+    assert close(arc.start_angle, 1.44)
+    assert close(arc.end_angle, 3.14)
+    assert not arc.is_circle
+
+
+def test_create_from_circle(frame):
+    circle = Circle(Plane(frame.point, frame.zaxis), 34.222)
+    arc = Arc.from_circle(circle, 0.1, 0.443)
+
+    assert close(arc.radius, circle.radius)
+    assert close(arc.angle, 0.343)
+    assert close(arc.circumference, circle.circumference)
+    assert close(arc.diameter, circle.diameter)
+    assert arc.center == circle.center
+
+
+def test_create_from_circle_partial(frame):
+    circle = Circle(Plane(frame.point, frame.zaxis), 34.222)
+    arc = Arc.from_circle(circle, 0.1, 0.443)
+
+    assert not arc.is_circle
+
+
+def test_create_from_circle_full(frame):
+    circle = Circle(Plane(frame.point, frame.zaxis), 34.222)
+    arc = Arc.from_circle(circle, 0.0, 2.0 * math.pi)
+
+    assert close(arc.start_angle, 0.0)
+    assert close(arc.angle, 2.0 * math.pi)
+    assert arc.is_circle
+
+
+def test_create_invalid_arc(frame):
+    with pytest.raises(ValueError):
+        _ = Arc(frame, 0.2314, 7.14)