Python Learning
Bill
BILL_NOSPAM at Noway.net
Mon Dec 18 19:05:56 EST 2017
Christian Gollwitzer wrote:
>
> You don't need to explain a vtable to explain dynamic_cast. Only if
> you want to become a compiler writer. It is not even required, vtables
> are just the most common implementation.
>
> dynamic_cast simply checks if the actual object that the pointer
> points to is an instance of a derived class, and then casts it into
> that. You could "explain" it with the following pseudo-code
>
> template <T*, base*>
> T* dynamic_cast<T*>(base *input) {
> if (isinstanceof(base, *input)) { return (T*)input; }
> else { return nullptr; }
> }
>
> How that works (particularly the "isinstanceof") is not the business
> of the programmer - it is sufficient to know that the compiler
> somewhere stores this information for every object.
>
> Christian
With that, the students would "boo you off the stage!"... and maybe
accuse you of being a "know it all". ; ) The point of college is
more about teaching students to think rather than in being efficient. I
have little doubt that a tech school could "get through everything" much
faster.
Bill
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