fixes sympy/sympy#9283: KroneckerDelta(p, 0) raises IndexError

diofant · Jul 3, 2015 · d1f9138 · d1f9138
1 parent 965cea5
commit d1f9138
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Showing 2 changed files with 3 additions and 5 deletions.
diff --git a/sympy/functions/special/tensor_functions.py b/sympy/functions/special/tensor_functions.py
@@ -158,12 +158,10 @@ def eval(cls, i, j):
             return cls(j, i)
 
         diff = Abs(i - j)
-        if diff == 0:
+        if diff.is_zero:
             return S.One
-        elif diff.is_number:
+        elif diff.is_positive:
             return S.Zero
-        elif i != 0 and diff.is_nonzero:
-            return cls(0, diff.args[0])
 
         if i.assumptions0.get("below_fermi") and \
                 j.assumptions0.get("above_fermi"):

diff --git a/sympy/functions/special/tests/test_tensor_functions.py b/sympy/functions/special/tests/test_tensor_functions.py
@@ -39,7 +39,7 @@ def test_kronecker_delta():
     assert KroneckerDelta(i, i + 1) == 0
     assert KroneckerDelta(0, 0) == 1
     assert KroneckerDelta(0, 1) == 0
-    assert KroneckerDelta(i + k, i) == KroneckerDelta(0, k)
+    assert KroneckerDelta(i + k, i) == 0
     assert KroneckerDelta(i + k, i + k) == 1
     assert KroneckerDelta(i + k, i + 1 + k) == 0
     assert KroneckerDelta(i, j).subs(dict(i=1, j=0)) == 0