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

[Gene <gene.ressler@gmail.com>]

On Oct 15, 7:03 pm, "Nasser M. Abbasi" <n...@12000.org> wrote:
> Ada experts:
>
> I am not able to find an example on this.
>
> I was wondering if in Ada I can initialize some array, where I can fill
> the content of each entry in the array based on some function of the index?
>
> For example, in Fortran one can do this:
> -----------------------
> program main
>    integer, parameter :: N = 10
>    real, dimension(N) :: a=(/(j**2,j=1,N)/)
>
>    print*, a
> end program
> ------------------------
> $ gfortran t3.f90
> $ ./a.exe
>     1.0000000       4.0000000       9.0000000       16.000000 etc....
>
> In Ada, what would I need to do in the initialization below?
> ---------------------------
> procedure t2 is
>     N: constant integer := 10;
>     a: array(1..N) of float := (others=>0.0); --??
> begin
>     null;
> end t2;
> -----------------------------
>
> I know ofcourse I can initialize it in the body by a loop, just wanted
> to see if it is possible to do it in the elaboration.

It's ugly, but you can get the effect with something like:

  Initializer_Index : Natural := 0;

  function Initial_Function_Of_Index return Float is
  begin
    Initializer_Index := Initializer_Index + 1;
    return 2.0 * Float(Initializer_Index);
  end;

  A : array(1 .. 100) of Float := (others =>
Initializer_Function_Of_Index);

What you're asking about is called a comprehension or list
comprehension. I agree it would be nice to have them.