Merge pull request #163 from skirpichev/is_comparable

Make Basic.is_comparable more conservative for extended_real's

sympy/core/basic.py

@@ -544,8 +544,8 @@ def is_hypergeometric(self, k):
 
     @property
     def is_comparable(self):
-        """Return True if self can be computed to a real number
-        with precision, else False.
+        """
+        Test if self can be computed to a real number with precision.
 
         Examples
         ========
@@ -562,15 +562,15 @@ def is_comparable(self):
         is_number = self.is_number
         if is_number is False:
             return False
-        if is_real and is_number:
-            return True
-        n, i = [p.evalf(2) for p in self.as_real_imag()]
+        n, i = self.as_real_imag()
+        if not (self.is_Float and self._prec == 1):  # workaround for skirpichev/omg#161
+            n, i = n.evalf(2), i.evalf(2)
         if not i.is_Number or not n.is_Number:
             return False
-        if i and i._prec > 1:
+        if i and (i._prec > 1 or i._prec == -1):
             return False
-        if not i and i._prec == -1:
-            if n._prec > 1:
+        if not i and (i._prec > 1 or i._prec == -1):
+            if n._prec > 1 or n._prec == -1:
                 return True
 
     @property

sympy/core/tests/test_basic.py

@@ -7,7 +7,7 @@
 from sympy.core.singleton import S, Singleton
 from sympy.core.symbol import symbols
 from sympy.core.compatibility import default_sort_key
-from sympy import sin, Lambda, Q
+from sympy import sin, cos, Lambda, Q
 
 
 b1 = Basic()
@@ -196,3 +196,8 @@ def test_literal_evalf_is_number_is_zero_is_comparable():
     assert i.is_zero
     assert i.is_number is False
     assert i.evalf(2, strict=False) == 0
+
+    # issue sympy/sympy#10272
+    n = sin(1)**2 + cos(1)**2 - 1
+    assert n.is_comparable is not True
+    assert n.n(2).is_comparable is not True