I found what I really want to realize has been asked in another previous post by myself:
In general, I just want a function to output the calculation procedure and then give some conclusive statements (such as displaying the result as a graph), but also the user can easily obtain the result of the function (such as through the most conventional assignment statement).
In fact, I seem to have used some Julia functions (such as some functions for machine learning or optimization) that do have similar effects. 