Tidy up ALEA RNG code

Not a performance improvement, just something that needed to be done.
Slightly simplifies the structure and removes useless functions
(changing the seed resets the RNG anyway - it is better to create a new
instance instead).

src/js/core/rng.js

@@ -1,129 +0,0 @@
-// ALEA RNG
-
-function Mash() {
-    var n = 0xefc8249d;
-    return function (data) {
-        data = data.toString();
-        for (var i = 0; i < data.length; i++) {
-            n += data.charCodeAt(i);
-            var h = 0.02519603282416938 * n;
-            n = h >>> 0;
-            h -= n;
-            h *= n;
-            n = h >>> 0;
-            h -= n;
-            n += h * 0x100000000; // 2^32
-        }
-        return (n >>> 0) * 2.3283064365386963e-10; // 2^-32
-    };
-}
-
-/**
- * @param {number|string} seed
- */
-function makeNewRng(seed) {
-    // Johannes Baagøe <baagoe@baagoe.com>, 2010
-    var c = 1;
-    var mash = Mash();
-    let s0 = mash(" ");
-    let s1 = mash(" ");
-    let s2 = mash(" ");
-
-    s0 -= mash(seed);
-    if (s0 < 0) {
-        s0 += 1;
-    }
-    s1 -= mash(seed);
-    if (s1 < 0) {
-        s1 += 1;
-    }
-    s2 -= mash(seed);
-    if (s2 < 0) {
-        s2 += 1;
-    }
-    mash = null;
-
-    var random = function () {
-        var t = 2091639 * s0 + c * 2.3283064365386963e-10; // 2^-32
-        s0 = s1;
-        s1 = s2;
-        return (s2 = t - (c = t | 0));
-    };
-
-    random.exportState = function () {
-        return [s0, s1, s2, c];
-    };
-
-    random.importState = function (i) {
-        s0 = +i[0] || 0;
-        s1 = +i[1] || 0;
-        s2 = +i[2] || 0;
-        c = +i[3] || 0;
-    };
-
-    return random;
-}
-
-export class RandomNumberGenerator {
-    /**
-     *
-     * @param {number|string=} seed
-     */
-    constructor(seed) {
-        this.internalRng = makeNewRng(seed || Math.random());
-    }
-
-    /**
-     * Re-seeds the generator
-     * @param {number|string} seed
-     */
-    reseed(seed) {
-        this.internalRng = makeNewRng(seed || Math.random());
-    }
-
-    /**
-     * @returns {number} between 0 and 1
-     */
-    next() {
-        return this.internalRng();
-    }
-
-    /**
-     * Random choice of an array
-     * @param {array} array
-     */
-    choice(array) {
-        const index = this.nextIntRange(0, array.length);
-        return array[index];
-    }
-
-    /**
-     * @param {number} min
-     * @param {number} max
-     * @returns {number} Integer in range [min, max[
-     */
-    nextIntRange(min, max) {
-        assert(Number.isFinite(min), "Minimum is no integer");
-        assert(Number.isFinite(max), "Maximum is no integer");
-        assert(max > min, "rng: max <= min");
-        return Math.floor(this.next() * (max - min) + min);
-    }
-
-    /**
-     * @param {number} min
-     * @param {number} max
-     * @returns {number} Number in range [min, max[
-     */
-    nextRange(min, max) {
-        assert(max > min, "rng: max <= min");
-        return this.next() * (max - min) + min;
-    }
-
-    /**
-     * Updates the seed
-     * @param {number} seed
-     */
-    setSeed(seed) {
-        this.internalRng = makeNewRng(seed);
-    }
-}

src/js/core/rng.ts

@@ -0,0 +1,81 @@
+class Alea {
+    private n = 0xefc8249d;
+    private c = 1;
+
+    private s0: number;
+    private s1: number;
+    private s2: number;
+
+    constructor(seed: string) {
+        // Johannes Baagøe <baagoe@baagoe.com>, 2010
+        this.s0 = this.mash(" ");
+        this.s1 = this.mash(" ");
+        this.s2 = this.mash(" ");
+
+        this.s0 -= this.mash(seed);
+        if (this.s0 < 0) {
+            this.s0 += 1;
+        }
+        this.s1 -= this.mash(seed);
+        if (this.s1 < 0) {
+            this.s1 += 1;
+        }
+        this.s2 -= this.mash(seed);
+        if (this.s2 < 0) {
+            this.s2 += 1;
+        }
+    }
+
+    protected next(): number {
+        const t = 2091639 * this.s0 + this.c * 2.3283064365386963e-10; // 2^-32
+        this.s0 = this.s1;
+        this.s1 = this.s2;
+        return (this.s2 = t - (this.c = t | 0));
+    }
+
+    private mash(data: string): number {
+        for (let i = 0; i < data.length; i++) {
+            this.n += data.charCodeAt(i);
+            let h = 0.02519603282416938 * this.n;
+            this.n = h >>> 0;
+            h -= this.n;
+            h *= this.n;
+            this.n = h >>> 0;
+            h -= this.n;
+            this.n += h * 0x100000000; // 2^32
+        }
+        return (this.n >>> 0) * 2.3283064365386963e-10; // 2^-32
+    }
+}
+
+export class RandomNumberGenerator extends Alea {
+    constructor(seed: string | number = Math.random()) {
+        super(seed.toString());
+    }
+
+    /**
+     * Random choice of an array
+     */
+    choice<T>(array: T[]): T {
+        const index = this.nextIntRange(0, array.length);
+        return array[index];
+    }
+
+    /**
+     * @returns Integer in range [min, max]
+     */
+    nextIntRange(min: number, max: number): number {
+        assert(Number.isFinite(min), "Minimum is no integer");
+        assert(Number.isFinite(max), "Maximum is no integer");
+        assert(max > min, "rng: max <= min");
+        return Math.floor(this.next() * (max - min) + min);
+    }
+
+    /**
+     * @returns Number in range [min, max]
+     */
+    nextRange(min: number, max: number): number {
+        assert(max > min, "rng: max <= min");
+        return this.next() * (max - min) + min;
+    }
+}