2D: do not return points outside the bounds, closes #181

Author: basnijholt

adaptive/learner/learner2D.py

@@ -543,7 +543,14 @@ def plot(self, n=None, tri_alpha=0):
                 n = int(0.658 / sqrt(areas(ip).min()))
                 n = max(n, 10)
 
-            x = y = np.linspace(-0.5, 0.5, n)
+            # The bounds of the linspace should be (-0.5, 0.5) but because of
+            # numerical precision problems it could (for example) be
+            # (-0.5000000000000001, 0.49999999999999983), then any point at exact
+            # boundary would be outside of the domain. See #181.
+            x_min, y_min = np.min(ip.points, axis=0)
+            x_max, y_max = np.max(ip.points, axis=0)
+            x = np.linspace(x_min, x_max, n)
+            y = np.linspace(y_min, y_max, n)
             z = ip(x[:, None], y[None, :] * self.aspect_ratio).squeeze()
 
             if self.vdim > 1: