Re: terminate applications

["Mark A. Biggar" <mark@biggar.org>]

Nick Roberts wrote:
> "Riccardo" <rfulcoli@amsjv.it> wrote in message
> news:bf5uks$8n0$1@e3k.asi.ansaldo.it...
> 
> 
>>is present a function that terminated applications?
>>if yes what's?
>>
>>for example: exit(0); // language C
> 
> 
> You should transfer control to the end of the main subprogram. For example:
> 
>    with Ada.Text_IO;
>    procedure Main is
>       Count: Natural := 0;
>       procedure Some_Inner_Procedure is
>          use Ada.Text_IO;
>       begin
>          Put_Line("Hello World");
>          if Count = 100 then
>             -- we want to terminate program here
>             goto End_of_Program;
>          end if;
>       end Some_Inner_Procedure;
>    begin
>       loop
>          Some_Inner_Procedure;
>          Count := Count + 1;
>       end loop; -- infinite loop
>    <<End_of_Program>> -- this is how you write a goto label in Ada
>    end Main;
> 
> This example doesn't necessarily show the most elegant technique, but it is
> generally acceptable, and illustrates the idea.
> 
> Of course, the best technique is always to let the program flow naturally to
> the end of the main subprogram, if it is reasonable to do so. To illustrate
> this, the above example would certainly be better rewritten like this:
> 
>    with Ada.Text_IO;
>    procedure Main is
>       procedure Some_Inner_Procedure is
>          use Ada.Text_IO;
>       begin
>          Put_Line("Hello World");
>       end Some_Inner_Procedure;
>    begin
>       for i in 1..100 loop
>          Some_Inner_Procedure;
>       end loop;
>    end Main;
> 
> I think it is quite important that, normally, you do not use any other
> method to terminate an Ada program, since using another method could prevent
> library packages (e.g. Ada.Text_IO, used in my examples) from finalizing
> ('cleaning up') properly.

If you really need to abort an Ada program form some deeply nested code,
raising an exception is a reaaonable way to do it.  All clean up actions
are guarenteed to happen and you can add a handler to the main procedure
to do any last gasp stuff cleanly.



-- 
mark@biggar.org
mark.a.biggar@comcast.net