Initial data commit

Task/Spiral-matrix/JavaScript/spiral-matrix-4.js

@@ -0,0 +1,88 @@
+(() => {
+    "use strict";
+
+    // ------------------ SPIRAL MATRIX ------------------
+
+    // spiral :: Int -> [[Int]]
+    const spiral = n => {
+        const go = (rows, cols, start) =>
+            Boolean(rows) ? [
+                enumFromTo(start)(start + pred(cols)),
+                ...transpose(
+                    go(
+                        cols,
+                        pred(rows),
+                        start + cols
+                    )
+                ).map(reverse)
+            ] : [
+                []
+            ];
+
+        return go(n, n, 0);
+    };
+
+
+    // ---------------------- TEST -----------------------
+    // main :: () -> String
+    const main = () => {
+        const
+            n = 5,
+            cellWidth = 1 + `${pred(n ** 2)}`.length;
+
+        return unlines(
+            spiral(n).map(
+                row => (
+                    row.map(x => `${x}`
+                    .padStart(cellWidth, " "))
+                )
+                .join("")
+            )
+        );
+    };
+
+
+    // --------------------- GENERIC ---------------------
+
+    // enumFromTo :: Int -> Int -> [Int]
+    const enumFromTo = m =>
+        n => Array.from({
+            length: 1 + n - m
+        }, (_, i) => m + i);
+
+
+    // pred :: Enum a => a -> a
+    const pred = x => x - 1;
+
+
+    // reverse :: [a] -> [a]
+    const reverse = xs =>
+        "string" === typeof xs ? (
+            xs.split("").reverse()
+            .join("")
+        ) : xs.slice(0).reverse();
+
+
+    // transpose :: [[a]] -> [[a]]
+    const transpose = rows =>
+        // The columns of the input transposed
+        // into new rows.
+        // Simpler version of transpose, assuming input
+        // rows of even length.
+        Boolean(rows.length) ? rows[0].map(
+            (_, i) => rows.flatMap(
+                v => v[i]
+            )
+        ) : [];
+
+
+    // unlines :: [String] -> String
+    const unlines = xs =>
+        // A single string formed by the intercalation
+        // of a list of strings with the newline character.
+        xs.join("\n");
+
+
+    // MAIN ---
+    return main();
+})();