Re: Possible for Ada 2020: "Cursors" for Arrays

[Niklas Holsti <niklas.holsti@tidorum.invalid>]

On 13-06-04 03:09 , Shark8 wrote:
> In a few threads a few people have expressed a desire
> to be able to initialize Arrays based on some formula
> usually including the indices. In order to do this we
> need some sort of "cursor"-type/attribute.

Maybe...

> So, let us propose a cursor-attribute so that some array
> type, T1, defined as
>   type T1 is Array( 1..10 ) of Integer;
> could have a variable initialized as follows:
>   V1 : T1:= (others => T1'Cursor'Index)
> resulting in V1 getting (1,2,3,4,5,6,7,8,9,10);

I think it would be better to build this ability from syntax similar to
the quantified expressions - "for all/some I in <range> => ...". To
avoid ambiguities when the array elements are Boolean we should use a
new keyword instead of "all" or "some". I would also not put this after
"others", but directly as an "array_component_association":

   V1 : T1 := (for each I in T1'Range => I);

But this would make yet another useful word ("each") reserved... Perhaps
we can do without any keyword:

   V1 : T1 := (for I in T1'Range => I);

> My question: does this look reasonable, or is it
> just superfluous?

Superfluous, yes, perhaps with the exception of some corner cases such
as initializing large systematic arrays during pre-elaboration. But nice
to have, why not.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .