Merge pull request #21928 from oscargus/fix21651

Fixed issue with determining is_integer for round functions (#21651)

sympy/concrete/tests/test_sums_products.py

@@ -1429,6 +1429,13 @@ def test_matrixsymbol_summation_numerical_limits():
     assert Sum(A**n*B**n, (n, 1, 3)).doit() == ans
 
 
+def test_issue_21651():
+    from sympy import floor, Sum, Symbol
+    i = Symbol('i')
+    a = Sum(floor(2*2**(-i)), (i, S.One, 2))
+    assert a.doit() == S.One
+
+
 @XFAIL
 def test_matrixsymbol_summation_symbolic_limits():
     N = Symbol('N', integer=True, positive=True)

sympy/core/mul.py

@@ -1351,7 +1351,7 @@ def _eval_is_integer(self):
                 b, e = a.as_base_exp()
                 if not b.is_integer or not e.is_integer: return
                 if e.is_negative:
-                    denominators.append(b)
+                    denominators.append(2 if a is S.Half else Pow(a, S.NegativeOne))
                 else:
                     # for integer b and positive integer e: a = b**e would be integer
                     assert not e.is_positive

sympy/core/tests/test_assumptions.py

@@ -1198,6 +1198,12 @@ def test_issue_17556():
     assert z.is_finite is False
 
 
+def test_issue_21651():
+    k = Symbol('k', positive=True, integer=True)
+    exp = 2*2**(-k)
+    assert exp.is_integer is None
+
+
 def test_assumptions_copy():
     assert assumptions(Symbol('x'), dict(commutative=True)
         ) == {'commutative': True}

sympy/functions/elementary/tests/test_integers.py

@@ -548,6 +548,12 @@ def test_issue_4149():
     assert floor(3 + E + pi*I + y*I) == 5 + floor(pi + y)*I
 
 
+def test_issue_21651():
+    k = Symbol('k', positive=True, integer=True)
+    exp = 2*2**(-k)
+    assert isinstance(floor(exp), floor)
+
+
 def test_issue_11207():
     assert floor(floor(x)) == floor(x)
     assert floor(ceiling(x)) == ceiling(x)