2016 Update

Task/Permutations/JavaScript/permutations-1.js

@@ -5,18 +5,18 @@ var d = document.getElementById('result');
 
 function perm(list, ret)
 {
-	if (list.length == 0) {
-		var row = document.createTextNode(ret.join(' ') + '\n');
-		d.appendChild(row);
-		return;
-	}
-	for (var i = 0; i < list.length; i++) {
-		var x = list.splice(i, 1);
-		ret.push(x);
-		perm(list, ret);
-		ret.pop();
-		list.splice(i, 0, x);
-	}
+    if (list.length == 0) {
+        var row = document.createTextNode(ret.join(' ') + '\n');
+        d.appendChild(row);
+        return;
+    }
+    for (var i = 0; i < list.length; i++) {
+        var x = list.splice(i, 1);
+        ret.push(x);
+        perm(list, ret);
+        ret.pop();
+        list.splice(i, 0, x);
+    }
 }
 
 perm([1, 2, 'A', 4], []);

Task/Permutations/JavaScript/permutations-2.js

@@ -1,30 +1,12 @@
-(function () {
+function perm(a) {
+    if (a.length < 2) return [a];
+    var c, d, b = [];
+    for (c = 0; c < a.length; c++) {
+        var e = a.splice(c, 1),
+            f = perm(a);
+        for (d = 0; d < f.length; d++) b.push([e].concat(f[d]));
+        a.splice(c, 0, e[0])
+    } return b
+}
 
-  // [a] -> [[a]]
-  function permutations(xs) {
-    return xs.length ? (
-               chain( xs,                            function (x)  {
-        return chain( permutations(deleted(x, xs)),  function (ys) {
-
-        return ( [[x].concat(ys)] );
-
-    })})) : [[]]
-  }
-
-  // monadic bind/chain for lists
-  function chain(xs, f) {
-    return [].concat.apply([], xs.map(f));
-  }
-
-  // drops first instance found
-  function deleted(x, xs) {
-    return xs.length ? (
-      x === xs[0] ? xs.slice(1) : [xs[0]].concat(
-        deleted(x, xs.slice(1))
-      )
-    ) : [];
-  }
-
-  return permutations(['Aardvarks', 'eat', 'ants'])
-
-})();
+console.log(perm(['Aardvarks', 'eat', 'ants']).join("\n"));

Task/Permutations/JavaScript/permutations-3.js

@@ -1 +1,6 @@
-[["Aardvarks", "eat", "ants"], ["Aardvarks", "ants", "eat"], ["eat", "Aardvarks", "ants"], ["eat", "ants", "Aardvarks"], ["ants", "Aardvarks", "eat"], ["ants", "eat", "Aardvarks"]]
+Aardvarks,eat,ants
+Aardvarks,ants,eat
+eat,Aardvarks,ants
+eat,ants,Aardvarks
+ants,Aardvarks,eat
+ants,eat,Aardvarks

Task/Permutations/JavaScript/permutations-4.js

@@ -0,0 +1,39 @@
+(function () {
+
+    // permutations :: [a] -> [[a]]
+    function permutations(xs) {
+        return xs.length ? (concatMap(
+            function (x) {
+                return concatMap(
+                    function (ys) {
+                        return ([[x].concat(ys)]);
+                    }, permutations(delete1(x, xs)))
+            }, xs)) : [[]]
+    }
+
+
+    // GENERIC LIBRARY FUNCTIONS
+
+    // concatMap :: (a -> [b]) -> [a] -> [b]
+    function concatMap(f, xs) {
+        return [].concat.apply([], xs.map(f));
+    }
+
+    // delete first instance of a in [a]
+    // delete1 :: a -> [a] -> [a]
+    function delete1(x, xs) {
+        return deleteBy(function (a, b) {
+            return a === b;
+        }, x, xs);
+    }
+
+    // deleteBy :: (a -> a -> Bool) -> a -> [a] -> [a]
+    function deleteBy(fnEq, x, xs) {
+        return xs.length ? fnEq(x, xs[0]) ? xs.slice(1) : [xs[0]]
+            .concat(deleteBy(fnEq, x, xs.slice(1))) : [];
+    }
+
+
+    return permutations(['Aardvarks', 'eat', 'ants'])
+
+})();

Task/Permutations/JavaScript/permutations-5.js

@@ -0,0 +1,3 @@
+[["Aardvarks", "eat", "ants"], ["Aardvarks", "ants", "eat"],
+ ["eat", "Aardvarks", "ants"], ["eat", "ants", "Aardvarks"],
+["ants", "Aardvarks", "eat"], ["ants", "eat", "Aardvarks"]]

Task/Permutations/JavaScript/permutations-6.js

@@ -0,0 +1,19 @@
+(function (lst) {
+    'use strict';
+
+    const permutations = (xs) => xs.length ? (
+            flatMap((x) => flatMap((xs) => [[x].concat(xs)],
+                permutations(del(x, xs))), xs)
+        ) : [[]],
+
+        flatMap = (f, xs) => [].concat.apply([], xs.map(f)),
+
+        del = (x, xs) => xs.length ? x === xs[0] ? (
+            xs.slice(1)
+        ) : [xs[0]].concat(del(x, xs.slice(1))
+        ) : [];
+
+
+    return permutations(lst);
+
+})(["Aardvarks", "eat", "ants"]);

Task/Permutations/JavaScript/permutations-7.js

@@ -0,0 +1,3 @@
+[["Aardvarks", "eat", "ants"], ["Aardvarks", "ants", "eat"],
+ ["eat", "Aardvarks", "ants"], ["eat", "ants", "Aardvarks"],
+["ants", "Aardvarks", "eat"], ["ants", "eat", "Aardvarks"]]