Re: [Q] Returning Strings From A Function

[bobduff@world.std.com (Robert A Duff)]

In article <33468b81.762963@news.demon.co.uk>,
John McCabe <john@assen.demon.co.uk> wrote:
>   File_Name : constant string := Text_IO.Name (File);

I don't remember if you were specifically asking about Ada 83, but Ada
95 also allows:

    File_Name : String := Text_IO.Name (File);

which allows you to change the characters of File_Name, but not its
length.

>type File_Name_Type is new String (1..12);
>
>then use:-
>
>procedure ...
>
>   File_Name : File_Name_Type;
>
>begin
>   :
>   File_Name := Text_IO.Name (File);
>   :
>end...
>
>or something similar. But unfortunately this is obviously not
>possible.

Did anyone suggest this:

    type String_Ptr is access String;

    procedure ...

       File_Name : String_Ptr;

    begin
       :
       File_Name := new String'(Text_IO.Name (File));
       :
    end...

?  Then you can change the length of the string by throwing away the old
one, and creating a new one on the heap.  In Ada 83, you have to worry
about storage management.  In Ada 95, you can encapsulate the storage
management using a controlled type -- and that's essentially what the
Strings.Unbounded package does.

- Bob