Re: Constant record components

["ME" <abcdefg@nonodock.net>]

"Craig Carey" <research@ijs.co.nz> wrote in message 
news:i04fb2t4vicb69kl55gsk1surko57g16vc@4ax.com...
>
> Fixing renames.
>
> On Fri, 14 Jul 2006 20:15:53 +1200, Craig Carey wrote:
>>On Fri, 7 Jul 2006 16:04:13 -0500, "Randy Brukardt" wrote:
> ...
>>>with them (only directly when the object is created), or you have to have
>>>some rule like "they're read-write in the body", which is what is
>>>disgusting. And remember that Initialize isn't the only routine of this
> ...
>
> A mispelling got partly towards converting jersey into jess, a leather
> strap sometimes attached to the leg of a hawk or falcon.
>
> At last check, Ada was not really making any progress at interfacing
> with C++, eg. in the following R.R would be written.
>
> generic
>   Debug : Integer;
> package R is
>   type R'Pkg_Type; --  Prevent an extra pass or "class package" etc.
> --  R could be a subtype if tagged for interfacing with C++.
>
>   type R'Pkg_Type (D : DT) is
>      record
>         A1 :    Integer;
>         A2 : in Integer;
>      end record;
>
>      --  "in" means that in the view of exterior code the value
>      --  can't be written to
I like it!
>
>   procedure Get_Val (X : out R, Fname : Str);
> end package R
>
> X  : R (Dbg => 0) (D => D1);
>
> procedure Main is
> begin
>   Get_Val (\ X, Fname => "abc.txt");
>   X.A2 := 9;  -- Syntax error.
>
> The Ada Reference Manual does not use enough words to say what
> "renames" should do. GNAT tries to know the memory addresses
> finalized inside of the declaration block.
>
> When often encountering the mistake, it seems that a
>
> K : Integer := 1;
> while K < 10 loop
>   declare
>      A  : Integer;
>      K  : constant;    --  Lock K down as a constant
>      E  : Element renames A (K);
>            --  Now it is clear E's address is now known
>   begin    --  K is constant
>      --  Actually making K constant after the begin would be safer
>
>
>
>
> Craig Carey