Re: Efficiently setting up large quantities of constant data

["Luke A. Guest" <laguest@n_o_p_o_r_k_a_n_d_h_a_m.abyss2.demon.co.uk>]

On Mon, 13 Dec 2004 13:48:49 -0800, Michael Mounteney wrote:

>      type structure is
>           record
>                part : component_ref;
>           end record;
> 
> So I will have lots of structures scattered about, which will be
> completely constant.  I would like to enforce this constancy, but Ada

Well, firstly, it seems like overkill to have a record which has only a
pointer to an array. Surely, just creating your variables *as* instances
of these arrays would be better?

> (as far as I know) does not (unlike C++;  that should get some hackles
> rising) allow `constant' to be splashed about in type definitions. This
> is on GNAT, which does not support pragma read_only.

By doing the above, you can of course do the following:

part : constant component_list := (...);  -- Initialise me here!!
 
> Is there any way to ensure that these data are not modified, other than
> by forbidding direct access to structure.part etc?

Do this with a package that *has memory* and it should work nicely. Also,
make it private if you want and add an accessor that can only read from
the arrays.

Luke.