reverts 46c2efd, closes issue python-quantities#100

ddale · ddale · commit 1948072e6e74 · 2015-12-17T16:40:59.000-05:00
diff --git a/quantities/tests/test_uncertainty.py b/quantities/tests/test_uncertainty.py
@@ -73,12 +73,6 @@ def test_uncertaintity_nanmean(self):
         b = UncertainQuantity([1,2,np.nan], 'm', [.1,.2,np.nan])
         self.assertQuantityEqual(a.mean(),b.nanmean())
 
-    def test_uncertainquantity_subtract(self):
-        a = UncertainQuantity(1, 'm', 1)
-        b = a.copy() # different object
-        self.assertQuantityEqual(a-a, UncertainQuantity(0, 'm', 0))
-        self.assertQuantityEqual(a-b, UncertainQuantity(0, 'm', np.sqrt(2)))
-
     def test_uncertainty_sqrt(self):
         a = UncertainQuantity([1,2], 'm', [.1,.2])
         self.assertQuantityEqual(a**0.5, a.sqrt())
diff --git a/quantities/uncertainquantity.py b/quantities/uncertainquantity.py
@@ -102,10 +102,7 @@ def __radd__(self, other):
     @scale_other_units
     def __sub__(self, other):
         res = super(UncertainQuantity, self).__sub__(other)
-        if self is not other:
-            u = (self.uncertainty**2+other.uncertainty**2)**0.5
-        else:
-            u = self.uncertainty*0
+        u = (self.uncertainty**2+other.uncertainty**2)**0.5
         return UncertainQuantity(res, uncertainty=u, copy=False)
 
     @with_doc(Quantity.__rsub__, use_header=False)
