100 lines
2.6 KiB
JavaScript
100 lines
2.6 KiB
JavaScript
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var exports = module.exports = function (xs) {
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if (typeof xs !== 'object') { // of which Arrays are
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throw new TypeError('Must be an Array or an object');
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}
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return Object.keys(exports).reduce(function (acc, name) {
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acc[name] = exports[name].bind(null, xs);
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return acc;
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}, {});
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};
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exports.shuffle = function (xs) {
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if (Array.isArray(xs)) {
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// uniform shuffle
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var res = xs.slice();
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for (var i = res.length - 1; i >= 0; i--) {
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var n = Math.floor(Math.random() * i);
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var t = res[i];
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res[i] = res[n];
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res[n] = t;
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}
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return res;
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}
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else if (typeof xs === 'object') {
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// weighted shuffle
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var weights = Object.keys(xs).reduce(function (acc, key) {
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acc[key] = xs[key];
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return acc;
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}, {});
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var ret = [];
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while (Object.keys(weights).length > 0) {
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var key = exports.pick(weights);
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delete weights[key];
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ret.push(key);
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}
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return ret;
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}
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else {
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throw new TypeError('Must be an Array or an object');
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}
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};
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exports.pick = function (xs) {
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if (Array.isArray(xs)) {
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// uniform sample
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return xs[Math.floor(Math.random() * xs.length)];
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}
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else if (typeof xs === 'object') {
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// weighted sample
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var weights = exports.normalize(xs);
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if (!weights) return undefined;
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var n = Math.random();
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var threshold = 0;
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var keys = Object.keys(weights);
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for (var i = 0; i < keys.length; i++) {
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threshold += weights[keys[i]];
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if (n < threshold) return keys[i];
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}
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throw new Error('Exceeded threshold. Something is very wrong.');
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}
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else {
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throw new TypeError('Must be an Array or an object');
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}
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};
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exports.normalize = function (weights) {
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if (typeof weights !== 'object' || Array.isArray(weights)) {
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throw 'Not an object'
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}
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var keys = Object.keys(weights);
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if (keys.length === 0) return undefined;
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var total = keys.reduce(function (sum, key) {
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var x = weights[key];
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if (x < 0) {
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throw new Error('Negative weight encountered at key ' + key);
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}
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else if (typeof x !== 'number') {
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throw new TypeError('Number expected, got ' + typeof x);
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}
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else {
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return sum + x;
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}
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}, 0);
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return total === 1
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? weights
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: keys.reduce(function (acc, key) {
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acc[key] = weights[key] / total;
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return acc;
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}, {})
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;
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};
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