* a fraction is zero if the numerator is zero and the denominator is not zero. \n* fix MachineReal.is_approx_zero

Author: mmatera

mathics/builtin/arithmetic.py

@@ -1346,6 +1346,11 @@ def apply(self, expr, evaluation):
 
         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)

mathics/core/evaluation.py

@@ -264,7 +264,6 @@ def __init__(
     def parse(self, query):
         "Parse a single expression and print the messages."
         from mathics.core.parser import SingleLineFeeder
-
         return self.parse_feeder(SingleLineFeeder(query))
 
     def parse_evaluate(self, query, timeout=None):
@@ -278,7 +277,6 @@ def parse_feeder(self, feeder):
     def parse_feeder_returning_code(self, feeder):
         "Parse a single expression from feeder and print the messages."
         from mathics.core.parser.util import parse_returning_code
-
         try:
             result, source_code = parse_returning_code(self.definitions, feeder)
         except TranslateError:

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):
@@ -2257,9 +2257,10 @@ def is_zero(self) -> bool:
 
     @property
     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
+        # In WMA, Chop[10.^(-10)] == 0,
+        # so, lets take it.
+        res = abs(self.value) <= 1e-10
+        return res
 
 
 class PrecisionReal(Real):