Family Day update

Task/Sierpinski-triangle/JavaScript/sierpinski-triangle-3.js

@@ -1,62 +1,24 @@
 (() => {
     'use strict';
 
-    // LINES OF SIERPINSKI TRIANGLE AT LEVEL N -------------------------------
+    // sierpinski :: Int -> String
+    const sierpinski = n =>
+        Array.from({
+            length: n
+        })
+        .reduce(
+            (xs, _, i) => {
+                const s = ' '.repeat(Math.pow(2, i));
+                return xs.map(x => s + x + s)
+                    .concat(
+                        xs.map(x => x + ' ' + x)
+                    )
+            },
+            ['*']
+        ).join('\n');
 
-    // sierpinski :: Int -> [String]
-    const sierpTriangle = n =>
-        // Previous triangle centered with left and right padding,
-        (n > 0) ? concat(ap([
-            map(xs => intercalate(xs, ap(
-                [s => concat(replicate(Math.pow(2, (n - 1)), s))], [' ', '-']
-            ))),
-
-            // above a pair of duplicates, placed one character apart.
-            map(xs => intercalate('+', [xs, xs]))
-        ], [sierpTriangle(n - 1)])) : ['▲'];
-
-
-    // GENERIC FUNCTIONS -----------------------------------------------------
-
-    // replicate :: Int -> a -> [a]
-    const replicate = (n, a) => {
-        let v = [a],
-            o = [];
-        if (n < 1) return o;
-        while (n > 1) {
-            if (n & 1) o = o.concat(v);
-            n >>= 1;
-            v = v.concat(v);
-        }
-        return o.concat(v);
-    };
-
-    // curry :: ((a, b) -> c) -> a -> b -> c
-    const curry = f => a => b => f(a, b);
-
-    // map :: (a -> b) -> [a] -> [b]
-    const map = curry((f, xs) => xs.map(f));
-
-    // Apply a list of functions to a list of arguments
-    // <*> :: [(a -> b)] -> [a] -> [b]
-    const ap = (fs, xs) => //
-        [].concat.apply([], fs.map(f => //
-            [].concat.apply([], xs.map(x => [f(x)]))));
-
-    // unlines :: [String] -> String
-    const unlines = xs => xs.join('\n');
-
-    // intercalate :: String -> [a] -> String
-    const intercalate = (s, xs) => xs.join(s);
-
-    // concat :: [[a]] -> [a] || [String] -> String
-    const concat = xs => {
-        if (xs.length > 0) {
-            const unit = typeof xs[0] === 'string' ? '' : [];
-            return unit.concat.apply(unit, xs);
-        } else return [];
-    };
-
-    // TEST ------------------------------------------------------------------
-    return unlines(sierpTriangle(4));
+    // TEST -------------------------------------------
+    console.log(
+        sierpinski(4)
+    );
 })();