Re: troubles learning OOP: expected type "Parent.Some_Child", found type Parent'Class

[Bojan Bozovic <bozovic.bojan@gmail.com>]

On Tuesday, February 13, 2018 at 2:32:42 AM UTC+1, Mehdi Saada wrote:
> I used to think that conversion from a class-wide type to a child type need t ever be explicit, I was wrong, and it's safer that way of course.
> It's better to use as little redispatching or dynamic whatever as possible. I did:
>  
> ELEMENT : Character renames STRING_VECTOR(Current_Index);
> case ELEMENT is
> when '(' => V_LOCAL (I) := new T_TOKEN_PARENTHESE'(La_Parenthese => '(');
> when ')' => V_LOCAL (I) := new T_TOKEN_PARENTHESE'(La_Parenthese => ')');
> when ';' => V_LOCAL (I) := new T_TOKEN_TERMINATEUR'(Le_Terminateur => ';');
> when '+' | '-' | '*' | '/' =>
>   V_LOCAL (I) := new T_Token_Operateur'(L_Operateur => T_Operateur'Value (STRING'(1 => ELEMENT)));
> 
> The last error (hope none more will pop up !) is
>       PUSH (PILE, To_Token(TEMP_PRIORITE.L_Operateur)'Access);
>       
> considered that 
> type PTR_TOKEN_CLASS is access constant T_Token'Class;
> package P_PILE_1 is new P_Pile_4 (T_Elem   => PTR_TOKEN_CLASS, Max_Pile => V_ENTREE'Length);
> use P_PILE_1, P_Pile_2;
> PILE : P_PILE_1.T_Pile(50);
> 
> I got "prefix of "Access" attribute must be aliased", which is logical, but how do I aliase the result of a conversion ?

You alias the function or procedure, for result to be a pointer, you can't return pointer directly. I don't see all your code but I can provide link

https://en.wikibooks.org/wiki/Ada_Programming/Types/access#Access_to_Subprogram

At least that seems to be a problem. Forgive me if I'm wrong.