Function flatten

libraries/p5.js:33798–33806

* turn a two dimensional array into one dimensional array * @param {Array} arr 2-dimensional array * @return {Array} 1-dimensional array * [[1, 2, 3],[4, 5, 6]] -> [1, 2, 3, 4, 5, 6]

(arr)

 * [[1, 2, 3],[4, 5, 6]] -> [1, 2, 3, 4, 5, 6]
 */
function flatten(arr){
  if (arr.length>0){
    return arr.reduce(function(a, b){
      return a.concat(b);
    });
  } else {
    return [];
  }
}

/**
 * turn a p5.Vector Array into a one dimensional number array