An implementation of the Bjorklund algorithm in JavaScript - Node.js Algorithm

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Description

An implementation of the Bjorklund algorithm in JavaScript

Demo Code


/*//from  w w w  .j  a va2s.c om
 
An implementation of the Bjorklund algorithm in JavaScript
 
Inspired by the paper 'The Euclidean Algorithm Generates Traditional Musical Rhythms' 
by Godfried Toussaint

This is a port of the original algorithm by E. Bjorklund which I
found in the paper 'The Theory of Rep-Rate Pattern Generation in the SNS Timing Systems' by
E. Bjorklund.
 
Jack Rutherford
 
*/

Array.prototype.rotate = (function() {
    // save references to array functions to make lookup faster
    var push = Array.prototype.push,
        splice = Array.prototype.splice;

    return function(count) {
        var len = this.length >>> 0, // convert to uint
            count = count >> 0; // convert to int

        // convert count to value in range [0, len[
        count = ((count % len) + len) % len;

        // use splice.call() instead of this.splice() to make function generic
        push.apply(this, splice.call(this, 0, count));
        return this;
    };
})();
 
function bjorklund(steps, pulses) {
  
  steps = Math.round(steps);
  pulses = Math.round(pulses);  
 
  if(pulses > steps || pulses == 0 || steps == 0) {
    return new Array();
  }
 
  pattern = [];
     counts = [];
     remainders = [];
     divisor = steps - pulses;
  remainders.push(pulses);
  level = 0;
 
  while(true) {
    counts.push(Math.floor(divisor / remainders[level]));
    remainders.push(divisor % remainders[level]);
    divisor = remainders[level]; 
         level += 1;
    if (remainders[level] <= 1) {
      break;
    }
  }
  
  counts.push(divisor);
 
  var r = 0;
  var build = function(level) {
    r++;
    if (level > -1) {
      for (var i=0; i < counts[level]; i++) {
        build(level-1); 
      }  
      if (remainders[level] != 0) {
            build(level-2);
      }
    } else if (level == -1) {
             pattern.push(0);  
    } else if (level == -2) {
           pattern.push(1);        
    } 
  };
 
  build(level);
  pattern = pattern.reverse();
  first_one = pattern.indexOf(1);
  if(first_one!=0){
    pattern.rotate(first_one)
  }
  return pattern
}

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