September 2017 Update

Task/Sorting-algorithms-Quicksort/JavaScript/sorting-algorithms-quicksort-6.js

@@ -1,33 +1,31 @@
-(function () {
+(() => {
     'use strict';
 
+    // QUICKSORT --------------------------------------------------------------
+
     // quickSort :: (Ord a) => [a] -> [a]
-    function quickSort(xs) {
-
-        if (xs.length) {
-            var h = xs[0],
-                [less, more] = partition(
-                    x => x <= h,
-                    xs.slice(1)
-                );
-
+    const quickSort = xs =>
+        xs.length > 1 ? (() => {
+            const
+                h = xs[0],
+                [less, more] = partition(x => x <= h, xs.slice(1));
             return [].concat.apply(
                 [], [quickSort(less), h, quickSort(more)]
             );
+        })() : xs;
 
-        } else return [];
-    }
 
+    // GENERIC ----------------------------------------------------------------
 
     // partition :: Predicate -> List -> (Matches, nonMatches)
     // partition :: (a -> Bool) -> [a] -> ([a], [a])
-    function partition(p, xs) {
-        return xs.reduce((a, x) => (
-                a[p(x) ? 0 : 1].push(x),
-                a
-            ), [[], []]);
-    }
+    const partition = (p, xs) =>
+        xs.reduce((a, x) =>
+            p(x) ? [a[0].concat(x), a[1]] : [a[0], a[1].concat(x)], [
+                [],
+                []
+            ]);
 
+    // TEST -------------------------------------------------------------------
     return quickSort([11.8, 14.1, 21.3, 8.5, 16.7, 5.7]);
-
 })();