Rationalize result that are an integer stay int

CHANGES.rst

@@ -42,6 +42,8 @@ Bugs
 
 * Fix and document better behavior of ``Quantile``
 * Improve Asymptote ``BezierCurve``implementation
+* ``Rationalize`` gives symmetric results for +/- like MMA does. If
+  the result is an integer, it stays that way.
 
 4.0.0
 -----

mathics/builtin/numeric.py

@@ -1311,7 +1311,7 @@ class Rationalize(Builtin):
 
     For negative $x$, '-Rationalize[-$x$] == Rationalize[$x$]' which gives symmetric results:
     >> Rationalize[-11.5, 1]
-    = -11 / 1
+    = -11
 
     Not all numbers can be well approximated.
     >> Rationalize[N[Pi]]
@@ -1412,11 +1412,11 @@ def apply_dx(self, x, dx, evaluation):
         if py_x.is_positive:
             a = self.approx_interval_continued_fraction(py_x - py_dx, py_x + py_dx)
             sym_x = sympy.ntheory.continued_fraction_reduce(a)
-            return Rational(sym_x)
         else:
             a = self.approx_interval_continued_fraction(-py_x - py_dx, -py_x + py_dx)
-            sym_x = sympy.ntheory.continued_fraction_reduce(a)
-            return Rational(-sym_x)
+            sym_x = -sympy.ntheory.continued_fraction_reduce(a)
+
+        return Integer(sym_x) if sym_x.is_integer else Rational(sym_x)
 
     @staticmethod
     def approx_interval_continued_fraction(xmin, xmax):

test/test_numeric.py

@@ -9,11 +9,10 @@ def test_rationalize():
             "Rationalize[42]",
             "42",
         ),
-        # We get 3 / 1 instead of 3
-        # (
-        #     "Rationalize[3, 1]",
-        #     "3",
-        # ),
+        (
+            "Rationalize[3, 1]",
+            "3",
+        ),
         (
             "Rationalize[N[Pi] + 0.8 I, 0]",
             "245850922 / 78256779 + 4 I / 5",