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Task/Sorting-algorithms-Quicksort/Fexl/sorting-algorithms-quicksort.fexl

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+# (sort keep compare xs) sorts the list xs using the three-way comparison
+# function.  It keeps duplicates if the keep flag is true, otherwise it
+# discards them and returns only the unique entries.
+
+\sort ==
+    (\keep\compare\xs
+    xs end \x\xs
+
+    \lo = (filter (\y compare y x T F F) xs)
+    \hi = (filter (\y compare y x F keep T) xs)
+
+    append (sort keep compare lo);
+    item x;
+    sort keep compare hi
+    )