Add "Package updates" section and fill in

CHANGES.rst

@@ -25,12 +25,17 @@ Performance
 
 * ``Blank*`` patterns without arguments are now singletons.
 
-API Incompatibility
+API incompatibility
 -------------
 
 * ``Matcher`` now requires an additional ``evaluation`` parameter
 
 
+Package updates
++++++++++++++++
+
+#. Python 3.12 is now supported
+#. SymPy 1.13 is now supported
 
 
 7.0.0

mathics/builtin/numeric.py

@@ -785,3 +785,59 @@ def eval(self, x, evaluation: Evaluation):
     def eval_error(self, x, seqs, evaluation: Evaluation):
         "Sign[x_, seqs__]"
         evaluation.message("Sign", "argx", Integer(len(seqs.get_sequence()) + 1))
+
+
+class UnitStep(Builtin):
+    """
+    <url>
+    :WMA link:
+    https://reference.wolfram.com/language/ref/UnitStep.html</url>)
+
+    <dl>
+      <dt>'Sign[$x$]'
+      <dd>return -1, 0, or 1 depending on whether $x$ is negative, zero, or positive.
+    </dl>
+
+    >> Unitize[E]
+     = 1
+    >> Sign[-6]
+     = -1
+    >> Sign[0]
+     = 0
+    >> Sign[{-5, -10, 15, 20, 0}]
+     = {-1, -1, 1, 1, 0}
+
+    For a complex number, 'Sign' returns the phase of the number:
+    >> Sign[3 - 4*I]
+     = 3 / 5 - 4 I / 5
+
+    """
+
+    summary_text = "turn number into 0 or 1"
+
+    attributes = A_LISTABLE | A_NUMERIC_FUNCTION | A_PROTECTED
+
+    messages = {
+        "argx": "Sign called with `1` arguments; 1 argument is expected.",
+    }
+
+    rules = {
+        "Sign[Power[a_, b_]]": "Power[Sign[a], b]",
+    }
+
+    def eval(self, x, evaluation: Evaluation):
+        "Sign[x_]"
+        result = eval_Sign(x)
+        if result is not None:
+            return result
+        # return None
+
+        sympy_x = x.to_sympy()
+        if sympy_x is None:
+            return None
+        # Unhandled cases. Use sympy
+        return super(Sign, self).eval(x, evaluation)
+
+    def eval_error(self, x, seqs, evaluation: Evaluation):
+        "Sign[x_, seqs__]"
+        evaluation.message("Sign", "argx", Integer(len(seqs.get_sequence()) + 1))