fixing bug (#300)

Co-authored-by: Monthly Tag bot <mtbot@noreply.github.com>

pina/geometry/cartesian.py

@@ -36,7 +36,7 @@ class CartesianDomain(Location):
         :return: Spatial variables defined in ``__init__()``
         :rtype: list[str]
         """
-        return list(self.fixed_.keys()) + list(self.range_.keys())
+        return sorted(list(self.fixed_.keys()) + list(self.range_.keys()))
 
     def update(self, new_domain):
         """Adding new dimensions on the ``CartesianDomain``

pina/geometry/ellipsoid.py

@@ -78,7 +78,7 @@ class EllipsoidDomain(Location):
         :return: Spatial variables defined in '__init__()'
         :rtype: list[str]
         """
-        return list(self.fixed_.keys()) + list(self.range_.keys())
+        return sorted(list(self.fixed_.keys()) + list(self.range_.keys()))
 
     def is_inside(self, point, check_border=False):
         """Check if a point is inside the ellipsoid domain.
@@ -279,7 +279,7 @@ class EllipsoidDomain(Location):
             return _single_points_sample(n, variables)
 
         if variables == "all":
-            variables = list(self.range_.keys()) + list(self.fixed_.keys())
+            variables = self.variables
 
         if mode in ["random"]:
             return _Nd_sampler(n, mode, variables)

pina/geometry/simplex.py

@@ -76,7 +76,7 @@ class SimplexDomain(Location):
 
     @property
     def variables(self):
-        return self._vertices_matrix.labels
+        return sorted(self._vertices_matrix.labels)
 
     def _build_cartesian(self, vertices):
         """