Re: index check failure - constraint error

[Adam Beneschan <adam@irvine.com>]

On Apr 1, 3:49 pm, Robert A Duff <bobd...@shell01.TheWorld.com> wrote:
> Jeffrey Carter <spam.jrcarter....@spam.not.acm.org> writes:
> > The idea that Strings always have a lower bound of 1 is quite common
> > among beginners.
>
> Whereas experts understand that it OUGHT to be true that
> "Strings always have a lower bound of 1", but it isn't true.
> It's a design flaw in the Ada language.
>
> > In SPARK all Strings do have a lower bound of 1.
>
> As they should.  It really makes things simpler.
> And (could be) more efficient.

I dunno.  I kind of like it that if I'm parsing a string, and I call

     Next_Item := Ada.Strings.Fixed.Index_Non_Blank (S
(Current_Index .. S'Last));

then Next_Item is the index of the actual character in S that I need,
and I don't need to add Current_Index to it and then think about
whether I need to add 1 or subtract 1 from the sum, as I'd have to do
something like that if Index_Non_Blank saw its Source parameter as a
string with a lower bound of 1.

                          -- Adam