Re: Initialization of Arrays in Ada

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

Ina Drescher wrote:
> Hi Ada Users,
>
> I have a question concerning the initialization of an array in Ada.
>
> For instance I have sth. like this:
>
> arr : Array (Integer Range<>) of Integer:=(1=>1, 2=>2);
>
> I just want to leave out the 1=> 2=> ...
>
> Is there any way like declating undefinite range arrays that ada does
> the counting work:
>
> In C in know this would be like this:
>
> char name[]="Test" and the compiler counts the number of characters.
>
> How is this done in Ada ?

Name : String := "Test";

> I know it's possible to count the number of entries for myself and
> then I could eliminate the 1=> ... so that it will look like this:
>
> arr : Array (Integer Range 1..2) of Integer:=(1, 2);

This works, and the following works too:

Arr : array (Positive range <>) := (1, 2);

But you should not create anonymous array types like that because that
would prevent you from passing Arr as a parameter to a subprogram.
Instead, you should declare a named type like so:

type A is array (Positive range <>) of Integer; -- named,
unconstrained type
My_Array : A := (1, 2); -- array constrained by its initial value

After that, My_Array is constrained; you cannot change its bounds
anymore; you can only change its contents:

My_Array := (3, 4); -- OK
My_Array := (5, 6, 7); -- Error, My_Array has only 2 components

HTH

--
Ludovic Brenta.