docs: public static double[] timesPlusEquals(final double[] v1, final double s1, final double[] v2) {
      assert v1.length == v2.length : ERR_VEC_DIMENSIONS;
      for(int i = 0; i < v1.length; i++) {
        v1[i] = v1[i] * s1 + v2[i];
      }
      return v1;
    }