mirror of
https://github.com/Tonejs/Tone.js
synced 2024-11-16 08:38:00 +00:00
ed71d8141b
no longer using AMD (require.js) style imports, and beginning to move to es6 "import/export" statements everywhere.
122 lines
3.3 KiB
JavaScript
122 lines
3.3 KiB
JavaScript
import Tone from "../core/Tone";
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/**
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* @class Tone.CtrlMarkov represents a Markov Chain where each call
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* to Tone.CtrlMarkov.next will move to the next state. If the next
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* state choice is an array, the next state is chosen randomly with
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* even probability for all of the choices. For a weighted probability
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* of the next choices, pass in an object with "state" and "probability" attributes.
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* The probabilities will be normalized and then chosen. If no next options
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* are given for the current state, the state will stay there.
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* @extends {Tone}
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* @example
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* var chain = new Tone.CtrlMarkov({
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* "beginning" : ["end", "middle"],
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* "middle" : "end"
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* });
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* chain.value = "beginning";
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* chain.next(); //returns "end" or "middle" with 50% probability
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*
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* @example
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* var chain = new Tone.CtrlMarkov({
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* "beginning" : [{"value" : "end", "probability" : 0.8},
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* {"value" : "middle", "probability" : 0.2}],
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* "middle" : "end"
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* });
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* chain.value = "beginning";
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* chain.next(); //returns "end" with 80% probability or "middle" with 20%.
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* @param {Object} values An object with the state names as the keys
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* and the next state(s) as the values.
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*/
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Tone.CtrlMarkov = function(values, initial){
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Tone.call(this);
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/**
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* The Markov values with states as the keys
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* and next state(s) as the values.
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* @type {Object}
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*/
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this.values = Tone.defaultArg(values, {});
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/**
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* The current state of the Markov values. The next
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* state will be evaluated and returned when Tone.CtrlMarkov.next
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* is invoked.
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* @type {String}
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*/
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this.value = Tone.defaultArg(initial, Object.keys(this.values)[0]);
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};
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Tone.extend(Tone.CtrlMarkov);
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/**
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* Returns the next state of the Markov values.
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* @return {String}
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*/
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Tone.CtrlMarkov.prototype.next = function(){
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if (this.values.hasOwnProperty(this.value)){
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var next = this.values[this.value];
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if (Tone.isArray(next)){
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var distribution = this._getProbDistribution(next);
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var rand = Math.random();
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var total = 0;
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for (var i = 0; i < distribution.length; i++){
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var dist = distribution[i];
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if (rand > total && rand < total + dist){
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var chosen = next[i];
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if (Tone.isObject(chosen)){
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this.value = chosen.value;
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} else {
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this.value = chosen;
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}
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}
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total += dist;
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}
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} else {
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this.value = next;
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}
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}
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return this.value;
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};
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/**
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* Choose randomly from an array weighted options in the form
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* {"state" : string, "probability" : number} or an array of values
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* @param {Array} options
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* @return {Array} The randomly selected choice
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* @private
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*/
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Tone.CtrlMarkov.prototype._getProbDistribution = function(options){
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var distribution = [];
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var total = 0;
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var needsNormalizing = false;
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for (var i = 0; i < options.length; i++){
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var option = options[i];
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if (Tone.isObject(option)){
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needsNormalizing = true;
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distribution[i] = option.probability;
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} else {
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distribution[i] = 1 / options.length;
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}
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total += distribution[i];
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}
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if (needsNormalizing){
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//normalize the values
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for (var j = 0; j < distribution.length; j++){
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distribution[j] = distribution[j] / total;
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}
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}
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return distribution;
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};
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/**
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* Clean up
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* @return {Tone.CtrlMarkov} this
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*/
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Tone.CtrlMarkov.prototype.dispose = function(){
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this.values = null;
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};
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export default Tone.CtrlMarkov;
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