code: public static double norm_inf(double[] a) {
      double max = Double.NEGATIVE_INFINITY;
      for (double d : a) {
        if (Math.abs(d) > max) {
          max = Math.abs(d);
        }
      }
      return max;
    }
docs: Computes inf-norm of vector
  
  @param a Array of double
  @return inf-norm of a