small fixes to PossibleZeroQ

Author: mmatera

mathics/builtin/arithmetic.py

@@ -1343,9 +1343,13 @@ class PossibleZeroQ(SympyFunction):
     def apply(self, expr, evaluation):
         "%(name)s[expr_]"
         from sympy.matrices.utilities import _iszero
-
         sympy_expr = expr.to_sympy()
         result = _iszero(sympy_expr)
+        if result is None:
+        # try expanding the expression
+            exprexp = Expression("ExpandAll", expr).evaluate(evaluation)
+            exprexp = exprexp.to_sympy()
+            result = _iszero(exprexp)
         if result is None:
             # Can't get exact answer, so try approximate equal
             numeric_val = Expression("N", expr).evaluate(evaluation)
@@ -1359,7 +1363,6 @@ def apply(self, expr, evaluation):
                     if Expression("Simplify", expr).evaluate(evaluation) == Integer(0)
                     else SymbolFalse
                 )
-
         return from_python(result)
 
 

mathics/core/expression.py

@@ -2109,7 +2109,7 @@ def __neg__(self) -> 'Rational':
 
     @property
     def is_zero(self) -> bool:
-        return self.numerator().is_zero
+        return self.numerator().is_zero and not(self.denominator().is_zero)
 
 
 class Real(Number):
@@ -2259,7 +2259,8 @@ def is_zero(self) -> bool:
     def is_approx_zero(self) -> bool:
         # FIXME: figure out how to hook int $MachinePrecision and
         # what the right definition here would be.
-        return abs(self.value) <= 10**-14
+        res = abs(self.value) <= 1e-14
+        return res
 
 
 class PrecisionReal(Real):