Starting random inplementation

ext/random/random.js

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+(function (root, factory) {
+    if (typeof define === 'function' && define.amd) {
+        define(['ramda'], factory);
+    } else if (typeof exports === 'object') {
+        module.exports = factory(require('../../ramda'));
+    } else {
+        root.Random = factory(root.ramda);
+    }
+}(this, function (R) {
+
+    // Random
+    // ----------
+    //
+    // TODO: (possibly?)
+    //     var random = new Random(seeds); // then...
+    //     random.nextInt(below): () -> random int, where 0 <= int < < below
+    //     random.intBetween(start, upTo): () -> random int, where start <= int < upTo
+    //     random.boolean(): () -> random boolean
+    //     random.fromChars(characters): int -> random String consisting of `int` chars drawn from `characters`.
+
+    // From http://baagoe.com/en/RandomMusings/javascript/
+    // mirrored at https://github.com/nquinlan/better-random-numbers-for-javascript-mirror
+    // Johannes Baagøe <baagoe@baagoe.com>, 2010
+    var Mash = function Mash() {
+        var n = 0xefc8249d;
+
+        var mash = 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
+        };
+
+        mash.version = 'Mash 0.9';
+        return mash;
+    };
+
+    // From http://baagoe.com/en/RandomMusings/javascript/
+    // mirrored at https://github.com/nquinlan/better-random-numbers-for-javascript-mirror
+    // Johannes Baagøe <baagoe@baagoe.com>, 2010
+    var Random = function Random() {
+        return (function (args) {
+            var s0 = 0;
+            var s1 = 0;
+            var s2 = 0;
+            var c = 1;
+
+            if (args.length == 0) {
+                args = [+new Date];
+            }
+            var mash = Mash();
+            s0 = mash(' ');
+            s1 = mash(' ');
+            s2 = mash(' ');
+
+            for (var i = 0; i < args.length; i++) {
+                s0 -= mash(args[i]);
+                if (s0 < 0) {
+                    s0 += 1;
+                }
+                s1 -= mash(args[i]);
+                if (s1 < 0) {
+                    s1 += 1;
+                }
+                s2 -= mash(args[i]);
+                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.uint32 = function () {
+                return random() * 0x100000000; // 2^32
+            };
+            random.fract53 = function () {
+                return random() +
+                    (random() * 0x200000 | 0) * 1.1102230246251565e-16; // 2^-53
+            };
+            random.version = 'Alea 0.9';
+            random.args = args;
+            return random;
+
+        }(Array.prototype.slice.call(arguments)));
+    };
+
+    // Returns a shuffled version of a list, using the
+    // [Fisher-Yates shuffle](http://en.wikipedia.org/wiki/Fisher–Yates_shuffle).
+    var shuffle = R.shuffle = function(random, list) {
+        var idx = -1;
+        var len = list.length;
+        var position;
+        var result = [];
+        while (++idx < len) {
+            position = Math.floor((idx + 1) * random());
+            result[idx] = result[position];
+            result[position] = list[idx];
+        }
+        return result;
+    };
+
+    R.Random = Random;
+
+    return Random;
+}));
+
+

ext/random/test/test.random.js

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+var assert = require('assert');
+var Lib = require('../../../ramda');
+var Random = require('../random');
+
+describe('Random', function() {
+    it('is a function', function()  {
+        assert.equal(typeof Random, 'function');
+    });
+
+    it('returns a function', function() {
+        assert.equal(typeof Random(), 'function');
+    });
+
+    it('returns consistent results for the same seeds', function() {
+        var random = new Random("my", 3, "seeds");
+        assert.equal(random(), 0.30802189325913787);
+        assert.equal(random(), 0.5190450621303171);
+        assert.equal(random(), 0.43635262292809784);
+    });
+
+    it('but returns entirely different results for even slightly different seeds', function() {
+        var random = new Random("my", 3, "weeds");
+        assert.equal(random(),  0.7021001486573368);
+        assert.equal(random(), 0.6134823360480368);
+        assert.equal(random(), 0.6507473199162632);
+    });
+});
+
+describe('shuffle', function() {
+    var shuffle = Lib.shuffle;
+    var random;
+
+    beforeEach(function() {
+        random = Random("my", 3, "seeds");
+    });
+
+    it('returns a shuffled copy of a list', function() {
+        var list = [1, 2, 3,4, 5, 6, 7, 8, 9, 10];
+        assert.deepEqual(shuffle(random, list), [6, 3, 4, 8, 5, 1, 7, 10, 2, 9]);
+    });
+
+});