enable mixed-unit addition and subtraction when units can be converted

ddale · ddale · commit 74ebd5c58d67 · 2009-10-12T17:36:10.000-04:00
diff --git a/.eric4project/quantities.e4q b/.eric4project/quantities.e4q
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE UserProject SYSTEM "UserProject-4.0.dtd">
 <!-- eric4 user project file for project quantities -->
-<!-- Saved: 2009-10-12, 12:46:11 -->
+<!-- Saved: 2009-10-12, 16:52:56 -->
 <!-- Copyright (C) 2009 ,  -->
 <UserProject version="4.0">
 </UserProject>
diff --git a/.eric4project/quantities.e4t b/.eric4project/quantities.e4t
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE Tasks SYSTEM "Tasks-4.2.dtd">
 <!-- eric4 tasks file for project quantities -->
-<!-- Saved: 2009-10-12, 12:46:11 -->
+<!-- Saved: 2009-10-12, 16:52:56 -->
 <Tasks version="4.2">
   <Task priority="1" completed="False" bugfix="False">
     <Summary>TODO: move to constants</Summary>
diff --git a/quantities/quantity.py b/quantities/quantity.py
@@ -47,12 +47,13 @@ def get_conversion_factor(from_u, to_u):
     assert from_u.dimensionality == to_u.dimensionality
     return from_u.magnitude / to_u.magnitude
 
-def protected_addition(f):
+def scale_other_units(f):
     @wraps(f)
     def g(self, other, *args):
         if not isinstance(other, Quantity):
             other = Quantity(other, copy=False)
-        getattr(self._dimensionality, f.__name__)(other._dimensionality)
+        if other._dimensionality != self._dimensionality:
+            other = other.rescale(self.units)
         return f(self, other, *args)
     return g
 
@@ -224,13 +225,33 @@ def __array_wrap__(self, obj, context=None):
             print 'https://bugs.launchpad.net/python-quantities'
         return result
 
+    @with_doc(np.ndarray.__add__)
+    @scale_other_units
+    def __add__(self, other):
+        return super(Quantity, self).__add__(other)
+
+    @with_doc(np.ndarray.__radd__)
+    @scale_other_units
+    def __radd__(self, other):
+        return super(Quantity, self).__radd__(other)
+
     @with_doc(np.ndarray.__iadd__)
-    @protected_addition
+    @scale_other_units
     def __iadd__(self, other):
         return super(Quantity, self).__iadd__(other)
 
+    @with_doc(np.ndarray.__sub__)
+    @scale_other_units
+    def __sub__(self, other):
+        return super(Quantity, self).__sub__(other)
+
+    @with_doc(np.ndarray.__rsub__)
+    @scale_other_units
+    def __rsub__(self, other):
+        return super(Quantity, self).__rsub__(other)
+
     @with_doc(np.ndarray.__isub__)
-    @protected_addition
+    @scale_other_units
     def __isub__(self, other):
         return super(Quantity, self).__isub__(other)
 
diff --git a/quantities/tests/test_25_quantity_arithmetic.py b/quantities/tests/test_25_quantity_arithmetic.py
@@ -126,6 +126,9 @@ def test_mul():
                     yield check(check_rmul, x, y)
         dtypes.pop(0)
 
+def test_mixed_addition():
+    assert_quantity_almost_equal(1*pq.ft + 1*pq.m, 4.280839895 * pq.ft)
+    assert_quantity_almost_equal(pq.ft + pq.m, 4.280839895 * pq.ft)
 
 #def test_negative():
 #    assert_array_equal(
diff --git a/quantities/tests/test_30_quantity_conversion.py b/quantities/tests/test_30_quantity_conversion.py
@@ -15,6 +15,15 @@ def test_quantity_creation():
     assert_raises(LookupError, pq.Quantity, 1, 'nonsense')
     assert_equal(str(pq.Quantity(1, '')), '1 dimensionless')
 
+def test_unit_conversion():
+    x = pq.Quantity(10., 'm')
+    x.units = pq.ft
+    assert_quantity_almost_equal(x, 32.80839895 * pq.ft)
+
+    x = 10 * pq.m
+    x.units = pq.ft
+    assert_quantity_almost_equal(x, 32.80839895 * pq.ft)
+
 def test_compound_reduction():
 
     pc_per_cc = pq.CompoundUnit("pc/cm**3")
diff --git a/quantities/uncertainquantity.py b/quantities/uncertainquantity.py
@@ -6,7 +6,7 @@
 import numpy as np
 
 from . import markup
-from .quantity import Quantity
+from .quantity import Quantity, scale_other_units
 from .registry import unit_registry
 from .utilities import with_doc
 
@@ -86,22 +86,26 @@ def __array_finalize__(self, obj):
         )
 
     @with_doc(Quantity.__add__, use_header=False)
+    @scale_other_units
     def __add__(self, other):
         res = super(UncertainQuantity, self).__add__(other)
         u = (self.uncertainty**2+other.uncertainty**2)**0.5
         return UncertainQuantity(res, uncertainty=u, copy=False)
 
     @with_doc(Quantity.__radd__, use_header=False)
+    @scale_other_units
     def __radd__(self, other):
         return self.__add__(other)
 
     @with_doc(Quantity.__sub__, use_header=False)
+    @scale_other_units
     def __sub__(self, other):
         res = super(UncertainQuantity, self).__sub__(other)
         u = (self.uncertainty**2+other.uncertainty**2)**0.5
         return UncertainQuantity(res, uncertainty=u, copy=False)
 
     @with_doc(Quantity.__rsub__, use_header=False)
+    @scale_other_units
     def __rsub__(self, other):
         if not isinstance(other, UncertainQuantity):
             other = UncertainQuantity(other, copy=False)
