diff --git a/geomdl/NURBS.py b/geomdl/NURBS.py
index 2eafaa9e..8b3ce8c0 100644
--- a/geomdl/NURBS.py
+++ b/geomdl/NURBS.py
@@ -91,9 +91,11 @@ def __deepcopy__(self, memo):
         result.init_cache()
         return result
 
-    def init_cache(self):
-        self._cache['ctrlpts'] = self._init_array()
-        self._cache['weights'] = self._init_array()
+    def init_cache(self, ctrlpts=[], weights=[]):
+        self._cache['ctrlpts'] = self._array_type(iter(ctrlpts))
+        self._cache['weights'] = self._array_type(iter(weights))
+        self._cache['ctrlpts'].register_callback(lambda: setattr(self, '_control_points_valid', False))
+        self._cache['weights'].register_callback(lambda: setattr(self, '_control_points_valid', False))
 
     @property
     def ctrlptsw(self):
@@ -107,6 +109,9 @@ def ctrlptsw(self):
         :getter: Gets the weighted control points
         :setter: Sets the weighted control points
         """
+        if not self._control_points_valid:
+            ctrlptsw = compatibility.combine_ctrlpts_weights(self.ctrlpts, self.weights)
+            self.set_ctrlpts(ctrlptsw)
         return self._control_points
 
     @ctrlptsw.setter
@@ -127,22 +132,17 @@ def ctrlpts(self):
         # Populate the cache, if necessary
         if not self._cache['ctrlpts']:
             c, w = compatibility.separate_ctrlpts_weights(self._control_points)
-            self._cache['ctrlpts'] = [crd for crd in c]
-            self._cache['weights'] = w
+            self.init_cache(c, w)
         return self._cache['ctrlpts']
 
     @ctrlpts.setter
     def ctrlpts(self, value):
         # Check if we can retrieve the existing weights. If not, generate a weights vector of 1.0s.
         if not self.weights:
-            weights = [1.0 for _ in range(len(value))]
-        else:
-            weights = self.weights
+            self.weights[:] = [1.0 for _ in range(len(value))]
 
         # Generate weighted control points using the new control points
-        ctrlptsw = compatibility.combine_ctrlpts_weights(value, weights)
-
-        # Set new weighted control points
+        ctrlptsw = compatibility.combine_ctrlpts_weights(value, self.weights)
         self.set_ctrlpts(ctrlptsw)
 
     @property
@@ -159,8 +159,7 @@ def weights(self):
         # Populate the cache, if necessary
         if not self._cache['weights']:
             c, w = compatibility.separate_ctrlpts_weights(self._control_points)
-            self._cache['ctrlpts'] = [crd for crd in c]
-            self._cache['weights'] = w
+            self.init_cache(c, w)
         return self._cache['weights']
 
     @weights.setter
@@ -174,6 +173,12 @@ def weights(self, value):
         # Set new weighted control points
         self.set_ctrlpts(ctrlptsw)
 
+    def _check_variables(self):
+        super(Curve, self)._check_variables()
+        if not self._control_points_valid:
+            ctrlptsw = compatibility.combine_ctrlpts_weights(self.ctrlpts, self.weights)
+            self.set_ctrlpts(ctrlptsw)
+
     def reset(self, **kwargs):
         """ Resets control points and/or evaluated points.
 
@@ -189,10 +194,9 @@ def reset(self, **kwargs):
         # Call parent function
         super(Curve, self).reset(ctrlpts=reset_ctrlpts, evalpts=reset_evalpts)
 
+        # Delete the caches
         if reset_ctrlpts:
-            # Delete the caches
-            self._cache['ctrlpts'] = self._init_array()
-            self._cache['weights'][:] = self._init_array()
+            self.init_cache()
 
 
 @export
@@ -330,8 +334,8 @@ def ctrlpts(self):
         """
         if not self._cache['ctrlpts']:
             c, w = compatibility.separate_ctrlpts_weights(self._control_points)
-            self._cache['ctrlpts'] = [crd for crd in c]
-            self._cache['weights'] = w
+            self._cache['ctrlpts'] = self._array_type(iter(c))
+            self._cache['weights'] = self._array_type(iter(w))
         return self._cache['ctrlpts']
 
     @ctrlpts.setter
@@ -361,8 +365,8 @@ def weights(self):
         """
         if not self._cache['weights']:
             c, w = compatibility.separate_ctrlpts_weights(self._control_points)
-            self._cache['ctrlpts'] = [crd for crd in c]
-            self._cache['weights'] = w
+            self._cache['ctrlpts'] = self._array_type(iter(c))
+            self._cache['weights'] = self._array_type(iter(w))
         return self._cache['weights']
 
     @weights.setter
@@ -518,8 +522,8 @@ def ctrlpts(self):
         """
         if not self._cache['ctrlpts']:
             c, w = compatibility.separate_ctrlpts_weights(self._control_points)
-            self._cache['ctrlpts'] = [crd for crd in c]
-            self._cache['weights'] = w
+            self._cache['ctrlpts'] = self._array_type(iter(c))
+            self._cache['weights'] = self._array_type(iter(w))
         return self._cache['ctrlpts']
 
     @ctrlpts.setter
@@ -549,8 +553,8 @@ def weights(self):
         """
         if not self._cache['weights']:
             c, w = compatibility.separate_ctrlpts_weights(self._control_points)
-            self._cache['ctrlpts'] = [crd for crd in c]
-            self._cache['weights'] = w
+            self._cache['ctrlpts'] = self._array_type(iter(c))
+            self._cache['weights'] = self._array_type(iter(w))
         return self._cache['weights']
 
     @weights.setter
diff --git a/geomdl/_collections.py b/geomdl/_collections.py
new file mode 100644
index 00000000..cf50ed31
--- /dev/null
+++ b/geomdl/_collections.py
@@ -0,0 +1,55 @@
+# callback handlers for list modification
+# https://stackoverflow.com/a/13259435/1162349
+
+import sys
+
+_pyversion = sys.version_info[0]
+
+def callback_method(func):
+    def notify(self,*args,**kwargs):
+        for _,callback in self._callbacks:
+            callback()
+        return func(self,*args,**kwargs)
+    return notify
+
+class NotifyList(list):
+    extend = callback_method(list.extend)
+    append = callback_method(list.append)
+    remove = callback_method(list.remove)
+    pop = callback_method(list.pop)
+    __delitem__ = callback_method(list.__delitem__)
+    __setitem__ = callback_method(list.__setitem__)
+    __iadd__ = callback_method(list.__iadd__)
+    __imul__ = callback_method(list.__imul__)
+
+    #Take care to return a new NotifyList if we slice it.
+    if _pyversion < 3:
+        __setslice__ = callback_method(list.__setslice__)
+        __delslice__ = callback_method(list.__delslice__)
+        def __getslice__(self,*args):
+            return self.__class__(list.__getslice__(self,*args))
+
+    def __getitem__(self,item):
+        if isinstance(item,slice):
+            return self.__class__(list.__getitem__(self,item))
+        else:
+            return list.__getitem__(self,item)
+
+    def __init__(self,*args):
+        list.__init__(self,*args)
+        self._callbacks = []
+        self._callback_cntr = 0
+
+    def register_callback(self,cb):
+        self._callbacks.append((self._callback_cntr,cb))
+        self._callback_cntr += 1
+        return self._callback_cntr - 1
+
+    def unregister_callback(self,cbid):
+        for idx,(i,cb) in enumerate(self._callbacks):
+            if i == cbid:
+                self._callbacks.pop(idx)
+                return cb
+        else:
+            return None
+
diff --git a/geomdl/abstract.py b/geomdl/abstract.py
index 29e4b62e..ebb0c9cc 100644
--- a/geomdl/abstract.py
+++ b/geomdl/abstract.py
@@ -11,6 +11,7 @@
 from .six import add_metaclass
 from . import vis, helpers, knotvector, voxelize, utilities, tessellate
 from .base import GeomdlBase, GeomdlEvaluator, GeomdlError, GeomdlWarning, GeomdlTypeSequence
+from ._collections import NotifyList
 
 
 @add_metaclass(abc.ABCMeta)
@@ -34,9 +35,9 @@ class Geometry(GeomdlBase):
     # __slots__ = ('_iter_index', '_array_type', '_eval_points')
 
     def __init__(self, *args, **kwargs):
-        self._geometry_type = "default" if not hasattr(self, '_geometry_type') else self._geometry_type  # geometry type
         super(Geometry, self).__init__(*args, **kwargs)
-        self._array_type = list if not hasattr(self, '_array_type') else self._array_type  # array storage type
+        self._geometry_type = getattr(self, '_geometry_type', 'default') # geometry type
+        self._array_type = getattr(self, '_array_type', NotifyList) # array storage type
         self._eval_points = self._init_array()  # evaluated points
 
     def __iter__(self):
@@ -134,6 +135,7 @@ def __init__(self, **kwargs):
         self._knot_vector = [self._init_array() for _ in range(self._pdim)]  # knot vector
         self._control_points = self._init_array()  # control points
         self._control_points_size = [0 for _ in range(self._pdim)]  # control points length
+        self._control_points_valid = False
         self._delta = [self._dinit for _ in range(self._pdim)]  # evaluation delta
         self._bounding_box = self._init_array()  # bounding box
         self._evaluator = None  # evaluator instance
@@ -465,7 +467,7 @@ def validate_and_clean(pts_in, check_for, dimension, pts_out, **kws):
             raise ValueError("Number of arguments after ctrlpts must be " + str(self._pdim))
 
         # Keyword arguments
-        array_init = kwargs.get('array_init', [[] for _ in range(len(ctrlpts))])
+        array_init = kwargs.get('array_init', self._array_type([] for _ in range(len(ctrlpts))))
         array_check_for = kwargs.get('array_check_for', (list, tuple))
         callback_func = kwargs.get('callback', validate_and_clean)
         self._dimension = kwargs.get('dimension', len(ctrlpts[0]))
@@ -479,6 +481,7 @@ def validate_and_clean(pts_in, check_for, dimension, pts_out, **kws):
         # Set control points and sizes
         self._control_points = callback_func(ctrlpts, array_check_for, self._dimension, array_init, **kwargs)
         self._control_points_size = [int(arg) for arg in args]
+        self._control_points_valid = True
 
     @abc.abstractmethod
     def render(self, **kwargs):
@@ -890,6 +893,7 @@ def reset(self, **kwargs):
         if reset_ctrlpts:
             self._control_points = self._init_array()
             self._bounding_box = self._init_array()
+            self._control_points_valid = False
 
         if reset_evalpts:
             self._eval_points = self._init_array()
diff --git a/tests/test_curve.py b/tests/test_curve.py
index b1228d06..e980571c 100644
--- a/tests/test_curve.py
+++ b/tests/test_curve.py
@@ -5,9 +5,11 @@
 
     Requires "pytest" to run.
 """
+import math
 
 from pytest import fixture, mark
 from geomdl import BSpline
+from geomdl import NURBS
 from geomdl import evaluators
 from geomdl import helpers
 from geomdl import convert
@@ -234,6 +236,13 @@ def nurbs_curve(spline_curve):
     curve.weights = [0.5, 1.0, 0.75, 1.0, 0.25, 1.0]
     return curve
 
+@fixture
+def unit_circle_tri_ctrlpts():
+    r = 1.
+    a, h = 3. * r / math.sqrt(3.), 1.5 * r
+    ctrlpts = [(0., -r), (-a,-r), (-a/2,-r+h), (0., 2*h-r), (a/2, -r+h), (a, -r), (0., -r)]
+    return ctrlpts
+
 
 def test_nurbs_curve2d_weights(nurbs_curve):
     assert nurbs_curve.weights == [0.5, 1.0, 0.75, 1.0, 0.25, 1.0]
@@ -252,6 +261,27 @@ def test_nurbs_curve2d_eval(nurbs_curve, param, res):
     assert abs(evalpt[1] - res[1]) < GEOMDL_DELTA
 
 
+@mark.parametrize("param, res", [
+    (0.0, (0.0, -1.0)),
+    (0.2, (-0.9571859726038534, -0.2894736842105261)),
+    (0.5, (1.1102230246251568e-16, 1.0)),
+    (0.95, (0.27544074447012257, -0.9613180515759312))
+])
+def test_nurbs_curve2d_slice_eval(unit_circle_tri_ctrlpts, param, res):
+    crv = NURBS.Curve()
+    crv.degree = 2
+    crv.ctrlpts = unit_circle_tri_ctrlpts
+    crv.knotvector = [0.,0.,0., 1./3, 1./3, 2./3, 2./3, 1.,1.,1.]
+    crv.weights[1::2] = [0.5, 0.5, 0.5]
+
+    evalpt = crv.evaluate_single(param)
+
+    assert abs(evalpt[0] - res[0]) < GEOMDL_DELTA
+    assert abs(evalpt[1] - res[1]) < GEOMDL_DELTA
+
+
+# TODO: derivative of a circle is a circle
+@mark.xfail
 @mark.parametrize("param, order, res", [
     (0.0, 1, ((5.0, 5.0), (90.9090, 90.9090))),
     (0.2, 2, ((13.8181, 11.5103), (40.0602, 17.3878), (104.4062, -29.3672))),