[fpc-pascal] private type and type compatibility

Martin lazarus at mfriebe.de
Wed Oct 30 14:40:10 CET 2013

On 30/10/2013 13:30, Xiangrong Fang wrote:
> 2013/10/30 Jonas Maebe <jonas.maebe at elis.ugent.be 
> <mailto:jonas.maebe at elis.ugent.be>>
>     The tdynarray type is not visible in the program because u1 is not
>     in its uses clause (it's not in scope whatsoever), and
>     nevertheless there is no problem to use it. It's of course not
>     exactly the same (tdynarray isn't declared as private to u1), but
>     at the scope visibility level it is the same situation as far as I
>     am concerned.
> I don't think they are the same.  tdynarray
>  is not usable in main program because you did not uses u1, NOT 
> because the type is defined as PRIVATE!
> As a matter of fact, if you define tdynarray as private (not in 
> interface section), there is no way you can use it as a return type of 
> an exported (public) function. This is a very consistent scoping rule!
> In my example, if the code is like this:
> generic TVector<T> = class
> private type
>   TDataType = array of T;
> private
>   function proc: TDataType;
> end;
> Then I think it is ok, because this PRIVATE type is used by PRIVATE 
> function.
> What do you think?

I think there is no problem with:

   a: array of Integer
   A:= obj.proc;

You are NOT using the type. You are using the value.

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