docs: public static void addVectors(double[] a1, double[] a2) {
  		 assert (a1 != null);
  		 assert (a2 != null);
  		 assert (a1.length == a2.length) : "Adding two arrays of different "
  			 + "length";
  
  		 for (int i = 0; i < a1.length; i++) {
  			 a1[i] += a2[i];
  		 }
  	 }