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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c++
Subject: Re: Tricky!
Date: Tue, 30 Jul 2019 07:31:59 -0700
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Tiib <ootiib@hot.ee> writes:

> On Monday, 29 July 2019 14:49:58 UTC+3, Bonita Montero  wrote:
>
>> I need a class-function / method that returns a function-pointer
>> to the same type of class-function.  How do I implement this?  I
>> need this to have a kind of state-machine where each state-func-
>> tion returns a pointer to the next state function.  I.e I would
>> write:  "while( (fn = state->*fn()) != nullptr );".  I see no way
>> to define the type of fn since it is recursive.
>
> Perhaps there are no way to make a function that return function
> pointer of its own type.  However I do not understand the need
> of it.  There is state and there is its handler and if you
> really need conversions between state and handler then you may
> make conversion constructors/operators ... but in my humble
> opinion it feels a bit messy and confusing.  Here is example:
>
>     #include <iostream>
>
>     // state
>     class State
>     {
>     public:
>         using Handler = State (*)(int);
>
>         State(Handler h)
>             :handler_(h)
>         { }
>
>         operator Handler() {return handler_;}
>
>     private:
>         Handler handler_;
>     };
>
>     // example handlers
>     State DoSomethingA(int param);
>
>     State DoSomethingB(int param);
>
>     // example of usage
>     int main()
>     {
>         State::Handler s(DoSomethingA(0));
>         s = s(1);
>         s = s(2);
>         s = s(3);
>         s = s(4);
>     }
>
>     // implementations of handlers
>     State DoSomethingA(int param)
>     {
>         std::cout << "A: " << param << '\n';
>         return DoSomethingB;
>     }
>
>     State DoSomethingB(int param)
>     {
>         std::cout << "B: " << param << '\n';
>         return DoSomethingA;
>     }

Did you not understand the question?  Your "solution"
doesn't do anything like what he is asking for.