September 2017 Update

Task/Sort-using-a-custom-comparator/JavaScript/sort-using-a-custom-comparator-2.js

@@ -0,0 +1,121 @@
+(function () {
+    'use strict';
+
+    // GENERIC FUNCTIONS FOR COMPARISONS
+
+    // Ordering :: ( LT | EQ | GT ) | ( -1 | 0 | 1 )
+
+    // compare :: a -> a -> Ordering
+    var compare = function (a, b) {
+        return a < b ? -1 : a > b ? 1 : 0;
+    };
+
+    // mappendOrdering :: Ordering -> Ordering -> Ordering
+    var mappendOrdering = function (a, b) {
+        return a !== 0 ? a : b;
+    };
+
+    // on :: (b -> b -> c) -> (a -> b) -> a -> a -> c
+    var on = function (f, g) {
+        return function (a, b) {
+            return f(g(a), g(b));
+        };
+    };
+
+    // flip :: (a -> b -> c) -> b -> a -> c
+    var flip = function (f) {
+        return function (a, b) {
+            return f.apply(null, [b, a]);
+        };
+    };
+
+    // arrayCopy :: [a] -> [a]
+    var arrayCopy = function (xs) {
+        return xs.slice(0);
+    };
+
+    // show :: a -> String
+    var show = function (x) {
+        return JSON.stringify(x, null, 2);
+    };
+
+    // TEST
+    var xs = ['Shanghai', 'Karachi', 'Beijing', 'Sao Paulo', 'Dhaka', 'Delhi', 'Lagos'];
+
+    var rs = [{
+        name: 'Shanghai',
+        pop: 24.2
+    }, {
+        name: 'Karachi',
+        pop: 23.5
+    }, {
+        name: 'Beijing',
+        pop: 21.5
+    }, {
+        name: 'Sao Paulo',
+        pop: 24.2
+    }, {
+        name: 'Dhaka',
+        pop: 17.0
+    }, {
+        name: 'Delhi',
+        pop: 16.8
+    }, {
+        name: 'Lagos',
+        pop: 16.1
+    }];
+
+    // population :: Dictionary -> Num
+    var population = function (x) {
+        return x.pop;
+    };
+
+    // length :: [a] -> Int
+    var length = function (xs) {
+        return xs.length;
+    };
+
+    // toLower :: String -> String
+    var toLower = function (s) {
+        return s.toLowerCase();
+    };
+
+    // lengthThenAZ :: String -> String -> ( -1 | 0 | 1)
+    var lengthThenAZ = function (a, b) {
+        return mappendOrdering(
+            on(compare, length)(a, b),
+            on(compare, toLower)(a, b)
+        );
+    };
+
+    // descLengthThenAZ :: String -> String -> ( -1 | 0 | 1)
+    var descLengthThenAZ = function (a, b) {
+        return mappendOrdering(
+            on(flip(compare), length)(a, b),
+            on(compare, toLower)(a, b)
+        );
+    };
+
+    return show({
+        default: arrayCopy(xs)
+            .sort(compare),
+
+        descendingDefault: arrayCopy(xs)
+            .sort(flip(compare)),
+
+        byLengthThenAZ: arrayCopy(xs)
+            .sort(lengthThenAZ),
+
+        byDescendingLengthThenZA: arrayCopy(xs)
+            .sort(flip(lengthThenAZ)),
+
+        byDescendingLengthThenAZ: arrayCopy(xs)
+            .sort(descLengthThenAZ),
+
+        byPopulation: arrayCopy(rs)
+            .sort(on(compare, population)),
+
+        byDescendingPopulation: arrayCopy(rs)
+            .sort(on(flip(compare), population))
+    });
+})();

Task/Sort-using-a-custom-comparator/JavaScript/sort-using-a-custom-comparator-3.js

@@ -0,0 +1,97 @@
+(() => {
+    'use strict';
+
+    // GENERIC FUNCTIONS FOR COMPARISONS
+
+    // Ordering :: ( LT | EQ | GT ) | ( -1 | 0 | 1 )
+    // compare :: a -> a -> Ordering
+    const compare = (a, b) => a < b ? -1 : (a > b ? 1 : 0);
+
+    // mappendOrdering :: Ordering -> Ordering -> Ordering
+    const mappendOrdering = (a, b) => a !== 0 ? a : b;
+
+    // on :: (b -> b -> c) -> (a -> b) -> a -> a -> c
+    const on = (f, g) => (a, b) => f(g(a), g(b));
+
+    // flip :: (a -> b -> c) -> b -> a -> c
+    const flip = f => (a, b) => f.apply(null, [b, a]);
+
+    // arrayCopy :: [a] -> [a]
+    const arrayCopy = (xs) => xs.slice(0);
+
+    // show :: a -> String
+    const show = x => JSON.stringify(x, null, 2);
+
+
+    // TEST
+    const xs = ['Shanghai', 'Karachi', 'Beijing', 'Sao Paulo', 'Dhaka', 'Delhi', 'Lagos'];
+
+    const rs = [{
+        name: 'Shanghai',
+        pop: 24.2
+    }, {
+        name: 'Karachi',
+        pop: 23.5
+    }, {
+        name: 'Beijing',
+        pop: 21.5
+    }, {
+        name: 'Sao Paulo',
+        pop: 24.2
+    }, {
+        name: 'Dhaka',
+        pop: 17.0
+    }, {
+        name: 'Delhi',
+        pop: 16.8
+    }, {
+        name: 'Lagos',
+        pop: 16.1
+    }]
+
+    // population :: Dictionary -> Num
+    const population = x => x.pop;
+
+    // length :: [a] -> Int
+    const length = xs => xs.length;
+
+    // toLower :: String -> String
+    const toLower = s => s.toLowerCase();
+
+    // lengthThenAZ :: String -> String -> ( -1 | 0 | 1)
+    const lengthThenAZ = (a, b) =>
+        mappendOrdering(
+            on(compare, length)(a, b),
+            on(compare, toLower)(a, b)
+        );
+
+    // descLengthThenAZ :: String -> String -> ( -1 | 0 | 1)
+    const descLengthThenAZ = (a, b) =>
+        mappendOrdering(
+            on(flip(compare), length)(a, b),
+            on(compare, toLower)(a, b)
+        );
+
+    return show({
+        default: arrayCopy(xs)
+            .sort(compare),
+
+        descendingDefault: arrayCopy(xs)
+            .sort(flip(compare)),
+
+        byLengthThenAZ: arrayCopy(xs)
+            .sort(lengthThenAZ),
+
+        byDescendingLengthThenZA: arrayCopy(xs)
+            .sort(flip(lengthThenAZ)),
+
+        byDescendingLengthThenAZ: arrayCopy(xs)
+            .sort(descLengthThenAZ),
+
+        byPopulation: arrayCopy(rs)
+            .sort(on(compare, population)),
+
+        byDescendingPopulation: arrayCopy(rs)
+            .sort(on(flip(compare), population))
+    });
+})();