Re: initialize an array (1-D) at elaboration using an expression based on the index?

[Georg Bauhaus <rm-host.bauhaus@maps.futureapps.de>]

On 11/10/10 4:51 PM, Adam Beneschan wrote:

>>     Jobs : array (Job_Id) of T := (for D in Job_Id =>  ???(D));
>>
>> ...

> ... But I think you can set up a function:
>
>     function Task_With_ID (Identity : Job_ID := No_Job) return T is
>     begin
>        return X : T(Identity);
>     end;
>
> and use that in your aggregate:
>
>     Single_Job : aliased Rec := (Task_With_ID(J), null);
>
> Warning: I have not tried this.

Tested with GNAT GPL 2010, it works.  In particular,

    Jobs : array (Job_Id) of T := (others => Make);

works, where construction function Make advances Job_Id
values for T's discriminant internally.  The setup is less
static, though.   The (for ...) syntax
will leave little doubt as to which index values Make
(or something in its place) is using to produce a T object.
That is not obvious  now.
(All as long a T can have a default discriminant.)

Just an ad-hoc idea:

    Jobs : array (X: Job_Id) of T := (others => Make(X));

where X: Job_Id is a little like a record discriminant
passed on to constrain components, for example,
only with a different "multiplicity".