Re: Lower bounds of Strings

[Egil H H <ehh.public@gmail.com>]

On Friday, January 15, 2021 at 6:35:54 PM UTC+1, Stephen Davies wrote:
> On Friday, 15 January 2021 at 11:41:24 UTC, J-P. Rosen wrote: 
> > function Slide (S : String) return String is 
> > (S(S'First) & S (S'First+1 .. S'Last));
> To me, this is a fundamental enough operation that, in the absence of 
> being able to specify a subtype where it happens automatically, it at 
> least deserves to be an attribute. But then again, I also think that 
> the attribute Trim_Image should be added, and I know you disagree 
> with me on that too :-)

Not entirely automatically, but you can do something like this:

...

   procedure Foo(Item :in out String) is
      subtype Mono_String is String (1..Item'Length);
   
      procedure Inner_Foo(Item : in out Mono_String) is
      begin
         Ada.Text_IO.Put_Line(Positive'Image(Item'First) & Positive'Image(Item'Last));
         Item(1) := 'C';
      end Inner_Foo;

   begin
      Inner_Foo(Item);
   end Foo;

 ...

   Foobar : String := "Foobar";
begin
   Foo(Foobar(4..5));
   Ada.Text_IO.Put_Line(Foobar);
...