Deference question

Deference question

[Papandopulo]

Maybe simple question, but I am just starting with Ada.

I try to read an array from file using streams:

declare
  type X_Value is mod 2**8;
  type X_Buffer is array (Positive range <>) of X_Value;
  type X_Buffer_Access is access all X_Buffer;
  type X_Buffer_Sz is new X_Buffer (1 .. Positive(Q_Bytes));
  type X_Buffer_Sz_Access is access all X_Buffer_Sz;
  Buff    : X_Buffer_Sz_Access;
begin
  Buff := new X_Buffer_Sz;
  X_Buffer_Sz'Read (X_Stream, Buff'all);
end;

But gnat tells me:
attribute designator expected
on the dereference (Buff'all)

What's wrong ?

Thank you,
George

Re: Deference question

[Stephen Leake]

papand0pul0@yahoo.com (Papandopulo) writes:

> Maybe simple question, but I am just starting with Ada.
> 
> I try to read an array from file using streams:
> 
> declare
>   type X_Value is mod 2**8;
>   type X_Buffer is array (Positive range <>) of X_Value;
>   type X_Buffer_Access is access all X_Buffer;
>   type X_Buffer_Sz is new X_Buffer (1 .. Positive(Q_Bytes));
>   type X_Buffer_Sz_Access is access all X_Buffer_Sz;
>   Buff    : X_Buffer_Sz_Access;
> begin
>   Buff := new X_Buffer_Sz;
>   X_Buffer_Sz'Read (X_Stream, Buff'all);
> end;
> 
> But gnat tells me:
> attribute designator expected
> on the dereference (Buff'all)

You want Buff.all, not Buff'all.

the ' means the following identifier is an "attribute", like 'Read. 

But you want a dereference, which is .all

-- 
-- Stephe

Re: Deference question

[Martin Krischik]

On Wed, 26 Feb 2003 07:34:03 +0000, Papandopulo wrote:

> Maybe simple question, but I am just starting with Ada.
> 
> I try to read an array from file using streams:
> 
> declare
>   type X_Value is mod 2**8;
>   type X_Buffer is array (Positive range <>) of X_Value;
>   type X_Buffer_Access is access all X_Buffer;
>   type X_Buffer_Sz is new X_Buffer (1 .. Positive(Q_Bytes));
>   type X_Buffer_Sz_Access is access all X_Buffer_Sz;
>   Buff    : X_Buffer_Sz_Access;
> begin
>   Buff := new X_Buffer_Sz;
>   X_Buffer_Sz'Read (X_Stream, Buff'all);

Typo: it is .all but 'Access.

Ada does not need as many pointer. So unless there is a good reason
against it I would suggest:

  Buff    : X_Buffer_Sz;
begin
  X_Buffer_Sz'Read (X_Stream, Buff);

> end;
> 
> But gnat tells me:
> attribute designator expected
> on the dereference (Buff'all)
> 
> What's wrong ?

With regards

Martin

-- 
Martin Krischik
mailto://Martin@krischik.com
http://www.ada.krischik.com