Initial data commit

Task/Roman-numerals-Encode/JavaScript/roman-numerals-encode-4.js

@@ -0,0 +1,78 @@
+(() => {
+    "use strict";
+
+    // -------------- ROMAN INTEGER STRINGS --------------
+
+    // roman :: Int -> String
+    const roman = n =>
+        mapAccumL(residue =>
+            ([k, v]) => second(
+                q => 0 < q ? (
+                    k.repeat(q)
+                ) : ""
+            )(remQuot(residue)(v))
+        )(n)(
+            zip([
+                "M", "CM", "D", "CD", "C", "XC",
+                "L", "XL", "X", "IX", "V", "IV", "I"
+            ])([
+                1000, 900, 500, 400, 100, 90,
+                50, 40, 10, 9, 5, 4, 1
+            ])
+        )[1]
+        .join("");
+
+
+    // ---------------------- TEST -----------------------
+    // main :: IO ()
+    const main = () => (
+        [2016, 1990, 2008, 2000, 2020, 1666].map(roman)
+    ).join("\n");
+
+
+    // ---------------- GENERIC FUNCTIONS ----------------
+
+    // mapAccumL :: (acc -> x -> (acc, y)) -> acc ->
+    // [x] -> (acc, [y])
+    const mapAccumL = f =>
+        // A tuple of an accumulation and a list
+        // obtained by a combined map and fold,
+        // with accumulation from left to right.
+        acc => xs => [...xs].reduce(
+            (a, x) => {
+                const tpl = f(a[0])(x);
+
+                return [
+                    tpl[0],
+                    a[1].concat(tpl[1])
+                ];
+            },
+            [acc, []]
+        );
+
+
+    // remQuot :: Int -> Int -> (Int, Int)
+    const remQuot = m =>
+        n => [m % n, Math.trunc(m / n)];
+
+
+    // second :: (a -> b) -> ((c, a) -> (c, b))
+    const second = f =>
+        // A function over a simple value lifted
+        // to a function over a tuple.
+        // f (a, b) -> (a, f(b))
+        xy => [xy[0], f(xy[1])];
+
+
+    // zip :: [a] -> [b] -> [(a, b)]
+    const zip = xs =>
+        // The paired members of xs and ys, up to
+        // the length of the shorter of the two lists.
+        ys => Array.from({
+            length: Math.min(xs.length, ys.length)
+        }, (_, i) => [xs[i], ys[i]]);
+
+
+    // MAIN --
+    return main();
+})();