Re: Design help

["Steve" <nospam_steved94@comcast.net>]

>"Carroll, Andrew" <andrew.carroll@okstate.edu> wrote in message 
>news:mailman.116.1173480208.18371.comp.lang.ada@ada-france.org...
>I am trying to design (what I guess is) a database table adapter.  Yes,
>it is a master's course assignment.  The current design is to use a file
>and have one record per line.  My goal is to get each line to be
>"serialized" so I can read the whole line in bytes and then take chunks
>of it and "cast" those into objects.
>
>On this list from a previous poster I found:
>
>   type Byte is range 0..255;
>   for Byte'Size use 8;
>   package Byte_IO is new Sequential_IO(Byte);
>

This defines a scalar data type for bytes.  Ok so far.

>Does that mean I could define the record like:
>
>   type dbrecord is range 0..sum_of_sizes_of_attributes;
>   for dbrecord'size use sum_of_sizes_of_attributes;
>   package DBRecord_IO is new Sequential_IO(dbrecord);
>

This looks a bit odd.  Here a scalar range is called "dbrecord" is defined 
that may contain the values in the range of  0 to 
sum_of_sizes_of_attributes.

So, for example, if sum_of_sizes_of_attributes is 32, values of type 
dbrecord may be assigned values in the range of 0 to 32.  The representation 
clause for dbrecord'size use sum_of size_attributes indicates that the 
storage size for those values is 32 bits... So values in the range of 0 to 
32 are being stored in 32 bits... no problem with that, but I don't think it 
is what was intended.

>My next big question....
>
>If I had
>   myrec: dbrecord;
>   ...
>   Dbrecord := <some data>...
>   ...
>
>   X := dbrecord(33..70);  --what type is x here?
>   attribute := cast(X);  --how do I cast x to an 'class?
>
>
>Am I making any sense?
>

Not really.

I would suggest that you pick up a book on Ada.  It is a language worth 
learning.

Regards,
Steve
(The Duck)

>
>Andrew Carroll
>Software Services
>405-744-4943
>andrew.carroll@okstate.edu
>