June 2018 Update

Task/Multiplication-tables/JavaScript/multiplication-tables-4.js

@@ -0,0 +1,92 @@
+(() => {
+
+    // multTable :: Int -> Int -> [[String]]
+    const multTable = (m, n) => {
+        const xs = enumFromToInt(m, n);
+        return [
+            ['x', ...xs],
+            ...concatMap(
+                x => [
+                    [x, ...concatMap(
+                        y => y < x ? [''] : [x * y],
+                        xs
+                    )]
+                ],
+                xs
+            )
+        ];
+    };
+
+    // main :: () -> IO String
+    const main = () => {
+        return wikiTable(
+            multTable(1, 12), true,
+            'text-align:center;width:33em;height:33em;table-layout:fixed;'
+        );
+    };
+
+    // GENERIC FUNCTIONS -----------------------------------------------------
+
+    // Tuple (,) :: a -> b -> (a, b)
+    const Tuple = (a, b) => ({
+        type: 'Tuple',
+        '0': a,
+        '1': b
+    });
+
+    // Size of space -> filler Char -> String -> Centered String
+    // center :: Int -> Char -> String -> String
+    const center = (n, c, s) => {
+        const
+            qr = quotRem(n - s.length, 2),
+            q = qr[0];
+        return concat(concat([replicate(q, c), s, replicate(q + qr[1], c)]));
+    };
+
+    // concat :: [[a]] -> [a]
+    // concat :: [String] -> String
+    const concat = xs =>
+        xs.length > 0 ? (() => {
+            const unit = typeof xs[0] === 'string' ? '' : [];
+            return unit.concat.apply(unit, xs);
+        })() : [];
+
+    // concatMap :: (a -> [b]) -> [a] -> [b]
+    const concatMap = (f, xs) => [].concat.apply([], xs.map(f));
+
+    // enumFromToInt :: Int -> Int -> [Int]
+    const enumFromToInt = (m, n) =>
+        n >= m ? Array.from({
+            length: Math.floor(n - m) + 1
+        }, (_, i) => m + i) : [];
+
+    // map :: (a -> b) -> [a] -> [b]
+    const map = (f, xs) => xs.map(f);
+
+    // quotRem :: Int -> Int -> (Int, Int)
+    const quotRem = (m, n) => Tuple(Math.floor(m / n), m % n);
+
+    // replicate :: Int -> a -> [a]
+    const replicate = (n, x) =>
+        Array.from({
+            length: n
+        }, () => x);
+
+    // FORMATTING -------------------------------------------------------------
+
+    // wikiTable :: [[a]] -> Bool -> String -> String
+    const wikiTable = (rows, blnHeader, style) =>
+        '{| class="wikitable" ' + (
+            style ? 'style="' + style + '"' : ''
+        ) + rows.map((row, i) => {
+            const dlm = ((blnHeader && !i) ? '!' : '|');
+            return '\n|-\n' + dlm + ' ' + row.map(v =>
+                    typeof v !== 'undefined' ? v : ' '
+                )
+                .join(' ' + dlm + dlm + ' ');
+        })
+        .join('') + '\n|}';
+
+    // MAIN ------------------------------------------------------------------
+    return main();
+})();