Re: Lower bounds of Strings

["Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>]

On 1/5/21 12:57 PM, Dmitry A. Kazakov wrote:
> 
> This is a constraint, a meaningless and dangerous one:
> 
>     procedure Foo (X : Mono_String);
>     S : String := "abcdefgh";
> begin
>     Foo (S (2..S'Last)); -- Boom! Constraint_Error

Surely the slice would slide, as it does in

with Ada.Text_IO;

procedure Slider is
    subtype S7 is String (1 .. 7);

    procedure Foo (X : in S7);

    procedure Foo (X : in S7) is
       -- Empty
    begin -- Foo
       Ada.Text_IO.Put (Item => X (7) );
       Ada.Text_IO.New_Line;
    end Foo;

    S : constant String := "abcdefgh";
begin -- Slider
    Foo (X => S (2 .. 8) );
end Slider;

~/Code$ gnatmake -gnatan -gnato2 -O2 -fstack-check slider.adb
x86_64-linux-gnu-gcc-9 -c -gnatan -gnato2 -O2 -fstack-check slider.adb
x86_64-linux-gnu-gnatbind-9 -x slider.ali
x86_64-linux-gnu-gnatlink-9 slider.ali -O2 -fstack-check
~/Code$ ./slider
h

-- 
Jeff Carter
"I'm a vicious jungle beast!"
Play It Again, Sam
131