allow None for any polygon side tangent

smichr · Mar 19, 2024 · d1de381 · d1de381
1 parent 9d13061
commit d1de381
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Showing 2 changed files with 20 additions and 7 deletions.
diff --git a/sympy/geometry/ellipse.py b/sympy/geometry/ellipse.py
@@ -694,7 +694,10 @@ def intersection(self, o):
             raise TypeError('Intersection not handled for %s' % func_name(o))
 
     def is_tangent(self, o):
-        """Is `o` tangent to the ellipse?
+        """Is `o` tangent to the ellipse? For a polygon return True if
+        all sides are tangent, None if any side is tangent, and False
+        if no side is tangent.
+        
 
         Parameters
         ==========
@@ -755,7 +758,17 @@ def is_tangent(self, o):
             else:
                 return False
         elif isinstance(o, Polygon):
-            return all(self.is_tangent(s) for s in o.sides)
+            hit = [0, 0]
+            for s in o.sides:
+                # is_tangent must raise if it can't decide;
+                # we are expecting True(1) or False(0) here
+                hit[self.is_tangent(s)] += 1
+            f, t = hit
+            if not f:
+                return True
+            if not t:
+                return False
+            return None
         elif isinstance(o, (LinearEntity3D, Point3D)):
             raise TypeError('Entity must be two dimensional, not three dimensional')
         else:

diff --git a/sympy/geometry/tests/test_ellipse.py b/sympy/geometry/tests/test_ellipse.py
@@ -471,19 +471,19 @@ def test_is_tangent():
     assert e1.is_tangent(Polygon((-3, 0), (3, 0), (0, 5))) is False
     assert e1.is_tangent(Polygon((-3, 0), (0, -5), (3, 0), (0, 5))) is False
     assert e1.is_tangent(Polygon((-3, -5), (-3, 5), (3, 5), (3, -5))) is True
-    assert c1.is_tangent(Polygon((-3, -5), (-3, 5), (3, 5), (3, -5))) is False
+    assert c1.is_tangent(Polygon((-3, -5), (-3, 5), (3, 5), (3, -5))) is None
     assert e1.is_tangent(Polygon((0, 0), (3, 0), (7, 7), (0, 5))) is False
-    assert e1.is_tangent(Polygon((3, 12), (3, -12), (6, 5))) is False
-    assert e1.is_tangent(Polygon((3, 12), (3, -12), (0, -5), (0, 5))) is False
+    assert e1.is_tangent(Polygon((3, 12), (3, -12), (6, 5))) is None
+    assert e1.is_tangent(Polygon((3, 12), (3, -12), (0, -5), (0, 5))) is None
     assert e1.is_tangent(Polygon((3, 0), (5, 7), (6, -5))) is False
     assert c1.is_tangent(Segment((0, 0), (-5, -2))) is False
     assert e1.is_tangent(Segment((-3, 0), (3, 0))) is False
     assert e1.is_tangent(Segment((-3, 5), (3, 5))) is True
     assert e1.is_tangent(Polygon((0, 0), (5, 5), (5, -5))) is False
     assert e1.is_tangent(Polygon((-100, -50), (-40, -334), (-70, -52))) is False
     assert e1.is_tangent(Polygon((-3, -5), (-3, 5), (3, 5), (3, -5))) is True
-    assert c1.is_tangent(Polygon((-3, -5), (-3, 5), (3, 5), (3, -5))) is False
-    assert e1.is_tangent(Polygon((3, 12), (3, -12), (0, -5), (0, 5))) is False
+    assert c1.is_tangent(Polygon((-3, -5), (-3, 5), (3, 5), (3, -5))) is None
+    assert e1.is_tangent(Polygon((3, 12), (3, -12), (0, -5), (0, 5))) is None
     assert e1.is_tangent(Polygon((3, 0), (5, 7), (6, -5))) is False
     raises(TypeError, lambda: e1.is_tangent(Point(0, 0, 0)))
     raises(TypeError, lambda: e1.is_tangent(Rational(5)))