Re: Community Input for the Maintenance and Revision of the Ada Programming Language

["Johan Söderlind Åström" <johaa1993@gmail.com>]

> 2. Allow a special indexing syntax, that I called relative indexing. Adding a Unary + operator (that has no other purpose ! :-) ) in front of an index expression means starting from A'First. Unary plus would then become the ordinal operator.
> 
>  A(+i) simply means A(A'First +i). 
> 
> This is an elegant and above all retro-compatible way of permitting to start every array at zero which is easier in algorithms, cf. Dijkstra (EWD 831 "Why numbering should start at zero") or Wirth's Oberon. Using A'Range is not possible outside the basic cases. Anytime you want to compute indexes you fall on relative indexes from 0 to N-1 and convoluted expressions that add or suppress A'First.

I usually cast a array to array that starts at zero index when implementing algorithms.

type Integer_Array is array (Integer range <>) of Integer;

procedure Algorithm (Item : Integer_Array) is
  use Ada.Assertions;
  X : Integer_Array (0 .. Item'Length - 1) with Address => Item'Address;
begin
  for I in 0 .. Item'Length - 1 loop
    Assert (X (I) = Item (Item'First + I));
  end loop;
end Algorithm;