Re: is Vax addressing sane today

On Wed, 25 Sep 2024 17:07:45 +0000, Michael S wrote:

On Wed, 25 Sep 2024 09:54:17 -0700
Stephen Fuld <sfuld@alumni.cmu.edu.invalid> wrote:
>

On 9/10/2024 1:13 AM, Niklas Holsti wrote:
>

In the Ada case, the ability to declare array types with
programmer- chosen index types with bounded range, such as
range-bounded integers or enumerations, means that the compiler can
avoid indexing checks when the (sub)type of the index is known at
compile time to fit within the index range of the array.

>
I have always liked the idea of variable ranges able to be specified
in the language.  Besides the advantages you mentioned, it provides
more human "comprehensibility" (if the ranges are reasonably named)
i.e. better internal documentation, and it makes responding to
specification changes required later in the program life cycle easier
and less error prone, i.e. if the range has to change, you change it
in one place and don't risk missing making the change in some obscure
part of the program you forgot about.
>
>

>
The problem here is that arrays with fixed bounds were common when
Ada was conceived back in the mid 1970s. On general-purpose (as opposed
to embedded) computers they were already much rarer when Ada was shipped
in 1983. By late 1990s arrays with fixed bounds were rare exception
rather than rule.

It sounds like variable ranges (array indexes) would be becoming more
common, also.
Where "variable range" is a variable that is defined to have a
specified range, but from run to run the upper and lower bounds
can be modified without re-compilation.

Except, of course, for many types of embedded computers. But even that
is gradually changing. Very gradually.