RE: Zero_Fill pragma, other proposition

[Lionel.DRAGHI@fr.thalesgroup.com]

| -----Message d'origine-----
...
| > type Message is record
| >    Id   : Message_Id;
| >    Data : Byte_Stream;
| > end record;
| >
| > for Message use record
| >    Id    at 0 range 0 .. 7;
| >    Spare at 0 range 8 .. 15 := 0; --> ADDED
| >    Data  at 0 range 16 .. 65;
| > end record;
| >
...........................................................
| package P is
|    type Message is record
|       Id   : Message_ID;
|       Data : Byte_Stream;
|    end record;
| 
|    -- Primitive operations of Message go here
| private
|    type Representation is record
|       Id    : Message_ID;
|       Spare : Eight_Bits;
|       Data  : Byte_Stream;
|    end record;
| 
|    for Representation use record
|       Id    at 0 range 0 .. 7;
|       Spare at 0 range 8 .. 15;
|       Data  at 0 range 16 .. 65;
|    end record;
|    
|    function To_Rep (M : in Message) return Representation;
|    function To_Message (R : in Representation) return Message;
| end P;
| 
| 
| package body P is
|    function To_Rep (M : in Message) return Representation is
|    begin
|       return (Id => M.Id, Spare => 0, Data => R.Data);
|    end To_Rep;
| 
|    function To_Message (R : in Representation) return Message is
|    begin
|       return (Id => R.Id, Data => R.Data);
|    end To_Message;
| 
|    -- Primitive operations of Message convert to 
| Representation whenever
|    -- interfacing to hardware
| end P;
| 
| I realise that your proposal reduces the amount of work required to
| achieve this, but the current language does allow you to do what you
| want.
Yes, and the problem is not so common.
 
On the other hand:
- even on this small example, there is a big difference in required work
(about 1 line vs 20), and a body is required, 
- it betters representation details encapsulation,
- it's not a big deal to implement... OK, I don't know about this, but I
bet!

-- 
Lionel Draghi