Initial data commit

Task/Floyds-triangle/JavaScript/floyds-triangle-1.js

@@ -0,0 +1,121 @@
+(function () {
+    'use strict';
+
+    // FLOYD's TRIANGLE -------------------------------------------------------
+
+    // floyd :: Int -> [[Int]]
+    function floyd(n) {
+        return snd(mapAccumL(function (start, row) {
+            return [start + row + 1, enumFromTo(start, start + row)];
+        }, 1, enumFromTo(0, n - 1)));
+    };
+
+    // showFloyd :: [[Int]] -> String
+    function showFloyd(xss) {
+        var ws = map(compose([succ, length, show]), last(xss));
+        return unlines(map(function (xs) {
+            return concat(zipWith(function (w, x) {
+                return justifyRight(w, ' ', show(x));
+            }, ws, xs));
+        }, xss));
+    };
+
+
+    // GENERIC FUNCTIONS ------------------------------------------------------
+
+    // compose :: [(a -> a)] -> (a -> a)
+    function compose(fs) {
+        return function (x) {
+            return fs.reduceRight(function (a, f) {
+                return f(a);
+            }, x);
+        };
+    };
+
+    // concat :: [[a]] -> [a] | [String] -> String
+    function concat(xs) {
+        if (xs.length > 0) {
+            var unit = typeof xs[0] === 'string' ? '' : [];
+            return unit.concat.apply(unit, xs);
+        } else return [];
+    };
+
+    // enumFromTo :: Int -> Int -> [Int]
+    function enumFromTo(m, n) {
+        return Array.from({
+            length: Math.floor(n - m) + 1
+        }, function (_, i) {
+            return m + i;
+        });
+    };
+
+    // justifyRight :: Int -> Char -> Text -> Text
+    function justifyRight(n, cFiller, strText) {
+        return n > strText.length ? (cFiller.repeat(n) + strText)
+            .slice(-n) : strText;
+    };
+
+    // last :: [a] -> a
+    function last(xs) {
+        return xs.length ? xs.slice(-1)[0] : undefined;
+    };
+
+    // length :: [a] -> Int
+    function length(xs) {
+        return xs.length;
+    };
+
+    // map :: (a -> b) -> [a] -> [b]
+    function map(f, xs) {
+        return xs.map(f);
+    };
+
+    // 'The mapAccumL function behaves like a combination of map and foldl;
+    // it applies a function to each element of a list, passing an accumulating
+    // parameter from left to right, and returning a final value of this
+    // accumulator together with the new list.' (See hoogle )
+
+    // mapAccumL :: (acc -> x -> (acc, y)) -> acc -> [x] -> (acc, [y])
+    function mapAccumL(f, acc, xs) {
+        return xs.reduce(function (a, x) {
+            var pair = f(a[0], x);
+
+            return [pair[0], a[1].concat([pair[1]])];
+        }, [acc, []]);
+    };
+
+    // show ::
+    // (a -> String) f,  Num n =>
+    // a -> maybe f -> maybe n -> String
+    var show = JSON.stringify;
+
+    // snd :: (a, b) -> b
+    function snd(tpl) {
+        return Array.isArray(tpl) ? tpl[1] : undefined;
+    };
+
+    // succ :: Int -> Int
+    function succ(x) {
+        return x + 1;
+    };
+
+    // unlines :: [String] -> String
+    function unlines(xs) {
+        return xs.join('\n');
+    };
+
+    // zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
+    function zipWith(f, xs, ys) {
+        var ny = ys.length;
+        return (xs.length <= ny ? xs : xs.slice(0, ny))
+            .map(function (x, i) {
+                return f(x, ys[i]);
+            });
+    };
+
+    // TEST ( n=5 and n=14 rows ) ---------------------------------------------
+
+    return unlines(map(function (n) {
+        return showFloyd(floyd(n)) + '\n';
+    }, [5, 14]));
+})();