Re: Assignment of limited private types...

[adam@irvine.com (Adam Beneschan)]

"Theodore E. Dennison" <dennison@escmail.mmc.orl.com> writes:
>stevem@dcs.gla.ac.uk (Steve McGowan) wrote:
> >
> > I'd like to pass in a 'file_type' identifier into a task, make a local
> > copy of this identifier within the task, and then write text to this
> > file stream inside the task.
> > 
> > But I cannot do this since 'file_type' is limited private.
> > 
> > Any ideas how I can pass in this identifier, and to write to it
> > locally?
> > 
> 
> The reason people make types "limited private" is so users CAN'T 
> make local copies of the objects. If the designer wanted you to
> be able to make copies of file_type objects, she would have made
> the type "private".
> 
> If for some reason you HAVE to make a copy, you could use an 
> unchecked_conversion, but DO NOT DO THIS! Odds are very high that 
> you will not get the results you desire. Try something else.

I usually solve problems of this type by using pointers.  E.g.

        type file_type_p is access file_type;

Now, when you want to open and access a file:

        my_file := new file_type_p;
        text_io.open (my_file.all, ...);
        text_io.get_line (my_file.all, ...);
        etc.
        text_io.close (my_file.all);

and you can assign file_type_p objects and pass them as parameters to
your heart's content.

Hope this helps,
                                -- Adam