Re: Should exceeding the range of Integer wrap around a la C?

[Anh Vo <anhvofrcaus@gmail.com>]

On Monday, May 21, 2018 at 8:23:21 AM UTC-7, nrs...@gmail.com wrote:
> Hi all,
> 
> I'm brand-new to Ada coming from a Fortran & Python background - just starting to write some trivial tutorial programs. I'm trying to understand the output of following program (copied from the "Lovelace" Ada95 tutorial):
> 
> -- compute.adb
> -- Demonstrate a trivial procedure, with another nested inside.
> with Ada.Text_IO, Ada.Integer_Text_IO;
> use Ada.Text_IO, Ada.Integer_Text_IO;
> 
> procedure Compute is
>    
>    procedure Double(Item : in out Integer) is
>    begin -- procedure Double
>       Item := Item * 2;
>    end Double;
>    
>    X : Integer := 1; -- Local variable X of type Integer
>    
> begin -- procedure Compute
>    loop 
>       Put(X);
>       New_Line;
>       Double(X);
>    end loop;
> end Compute;
> 
> I expect this program to print powers of 2 until `X` exceeds the range of Integer. Instead, it seems to "wrap around" with the following (abbreviated) output:
>           1
>           2
>           4
>       [...]          
>   268435456
>   536870912
>  1073741824
> -2147483648
>           0
>           0
>       [...]
>           0
> 
> I am compiling with GNAT 4.9.2 on a Debian Linux system using `gnat make compute` with no further compiler flags. Are my expectations wrong, or is this incorrect behavior?

A Constraint_Error must be raised. If not, it is a compiler bug.

Anh Vo