docs: public static double[] minusTimes(final double[] v1, final double[] v2, final double s2) {
      assert v1.length == v2.length : ERR_VEC_DIMENSIONS;
      final double[] sub = new double[v1.length];
      for(int i = 0; i < v1.length; i++) {
        sub[i] = v1[i] - v2[i] * s2;
      }
      return sub;
    }