Initial data commit

Task/Department-numbers/JavaScript/department-numbers-4.js

@@ -0,0 +1,51 @@
+(() => {
+    "use strict";
+
+    // -------------- NUMBERING CONSTRAINTS --------------
+
+    // options :: Int -> Int -> Int -> [(Int, Int, Int)]
+    const options = lo => hi => total => {
+        const
+            bind = xs => f => xs.flatMap(f),
+            ds = enumFromTo(lo)(hi);
+
+        return bind(ds.filter(even))(
+            x => bind(ds.filter(d => d !== x))(
+                y => bind([total - (x + y)])(
+                    z => (z !== y && lo <= z && z <= hi) ? [
+                        [x, y, z]
+                    ] : []
+                )
+            )
+        );
+    };
+
+    // ---------------------- TEST -----------------------
+    const main = () => {
+        const
+            label = "(Police, Sanitation, Fire)",
+            solutions = options(1)(7)(12),
+            n = solutions.length,
+            list = solutions
+            .map(JSON.stringify)
+            .join("\n");
+
+        return (
+            `${label}\n\n${list}\n\nNumber of options: ${n}`
+        );
+    };
+
+    // ---------------- GENERIC FUNCTIONS ----------------
+
+    // enumFromTo :: Int -> Int -> [Int]
+    const enumFromTo = m =>
+        n => Array.from({
+            length: 1 + n - m
+        }, (_, i) => m + i);
+
+    // even :: Integral a => a -> Bool
+    const even = n => n % 2 === 0;
+
+    // MAIN ---
+    return main();
+})();