Re: Looping over a tagged record?

["DuckE" <nospam_steved94@home.com>]

I'll share a couple of idea's to explore:

 Idea 1)  Instead of defining the fields of the record as String_60,
Integer, etc..  Define each field as a descendent of a common object.  In
addition to the data fields, add an array of references to the fields.

Something along the lines of:
   type Field_Type is abstract tagged private;
   type Field_Type_Acc is access all Field_Type;
   type String_Field is new Field_Type with private;
   type Integer_Field is new Field_Type with private;
   type Field_List is array( Positive range <> ) of Field_Type_Acc;
   type Big_Record is tagged
     record
       A1 : aliased String_Field;
       A2 : aliased String_Field;
       N1 : aliased Integer_Field;
       Field_References : Field_List(1..3);
     end record;

Then at some point initialize "Field_References" to point to the fields
within the same object.  If Big_Record is derived from Ada.Finalization,
then Field_References may be initialized automatically.

  Idea 2) Keep your existing record definition, but define each field as
aliased.  Then create a list of objects where again each object descends
from the same base class, only now each different object contains a
reference to each of the field types.

Both of these approaches use the same basic theme of setting up an array
that gives you access to all elements using a common base class.  I believe
both of these approaches are "workable" but neither is particularly elegant
or pretty.

I hope this helps,
SteveD


"M R Goodwin" <mgoodwinSPAMMY@redrocketconsortium.com> wrote in message
news:9god9a$g04$0@208.164.98.151...
> Hi!
>
> This is a part practical, and a part 'I wonder' type problem.
> I have a tagged record that is pretty big.  Most, but not all of
> the elements in it are a bounded string type.  Because I don't feel
> like the typing and all I would need to do to assign and later change
> values, I was wondering if there is anyway to loop over all elements in
> the record, checking their type and then taking the right action...
>
> type Big_record is tagged record
> a1 : String_60;
> a2 : String_60;
> n1 : Integer;
> ...
> a30 : String_60;
> end record;
>
> And I want to do something like:
> (And yes, I know its not Ada code!)
> For I in ?number of elements? loop
> if I is Integer then Blah, blah
> elsif I is String_60 Blah, Blah.
> end;
>
>
> I've been messing around with it, and have not come to any workable
> solution.
>
> Thanks for the help,
>
> Matthew