Go over more builtin docs...

* `PowersRepresentations``
* ``ReverseSort``

Author: rocky

CHANGES.rst

@@ -88,6 +88,10 @@ By `@davidar <https://github.com/davidar>`_:
 ``mathics`` command line
 ++++++++++++++++++++++++
 
+Option ``--post-mortem`` was added which goes into the `trepan3k
+debugger <https https://pypi.org/project/trepan3k/>`_ on an
+unrecoverable error. This option is available on other front-ends..
+
 WMA Compatibility
 -----------------
 

mathics/builtin/numbers/numbertheory.py

@@ -831,10 +831,21 @@ class PowersRepresentations(Builtin):
       <dd>represent $n$ as a sum of $k$ non-negative integers raised to the power of $p$.
     </dl>
 
+    Get the ways licence plate number 1729 can be represented as the sum of two cubes:
     >> PowersRepresentations[1729, 2, 3]
      = {{1, 12}, {9, 10}}
-    >> PowersRepresentations[50, 3, 2]
-     = {{0, 1, 7}, {0, 5, 5}, {3, 4, 5}}
+
+    See <url>:1729:https://en.wikipedia.org/wiki/1729_(number)</url> for the full backstory.
+
+    Demonstrate the validity of the Pythagorian triple: 3^2 + 4^2 == 5^2
+    >> PowersRepresentations[25, 2, 2]
+     = {{0, 5}, {3, 4}}
+
+    Since 0 is allowed in the sum, 'PowersRepresentations[$n$, $k$+1, $p$]' is includes \
+   'PowersRepresentations[$n$, $k$, $p$]' with by inserting a zero element at the beginning:
+
+    >> PowersRepresentations[25, 3, 2]
+     = {{0, 0, 5}, {0, 3, 4}}
     """
 
     attributes = A_PROTECTED | A_READ_PROTECTED

mathics/builtin/statistics/orderstats.py

@@ -279,10 +279,21 @@ class ReverseSort(Builtin):
 
     >> ReverseSort[{c, b, d, a}]
      = {d, c, b, a}
+
+    You can specify a binary comparison function:
+    >> ReverseSort[{1, 2, 0, 3}, Less]
+     = {3, 2, 1, 0}
+
+    Using 'Greater' for the above, reverses the reverse sort:
+    >> ReverseSort[{1, 2, 0, 3}, Greater]
+     = {0, 1, 2, 3}
+
+    See also <url>:Sort:
+    /doc/reference-of-built-in-symbols/descriptive-statistics/order-statistics/sort/</url>.
     """
 
     attributes = A_PROTECTED
-    summary_text = "reverse sort"
+    summary_text = "sort in reverse order"
 
     rules = {
         "ReverseSort[list_]": "Reverse[Sort[list]]",
@@ -318,10 +329,13 @@ class Sort(Builtin):
      = {2 + c_, 1 + b__}
     >> Sort[{x_ + n_*y_, x_ + y_}, PatternsOrderedQ]
      = {x_ + n_ y_, x_ + y_}
+
+    See also <url>:ReverseSort:
+    /doc/reference-of-built-in-symbols/descriptive-statistics/order-statistics/reversesort/</url>.
     """
 
     attributes = A_PROTECTED
-    summary_text = "sort lexicographically or with any comparison function"
+    summary_text = "sort lexicographically or with a comparison function"
 
     def eval(self, list, evaluation: Evaluation):
         "Sort[list_]"