Re: F9X twister & ADA (was: n-dim'l vectors)

[Geoff Bull <geoff@research.canon.com.au>]

James Giles wrote:

> >What about buffered io and user defined buffering?
> 
> Like all parts of the program's state, those are all still present
> *in* the debugging file.  You can inspect them there.

But I'd prefer it in a place defined by me!
I hate looking at core dumps and, thankfully, since using
Ada I *never* have to - same for Java. (when I was a C/Fortran I
lived in the debugger, I get the impression you are still stuck there )

In any embedded / real time context your proposal is just plain wrong.

Stop dead on exception would be difficult to implement if the
program is multithreaded or distributed across multiple machines?

> I think undocumented exceptions are clearly the ugliest way to
> accomplish this.

But there is nothing wrong with clearly documented exceptions?

> Any public property of a procedure which isn't
> explicitly declared - by direct requirement of the language
> definition - is probably a bad idea.

Are you saying this is ok:
(yes I know Start should return a boolean,
instead of raising an exception)

package Rocket_Motor is

   procedure Start;
   --  may raise Primary_Ignition_Failed

   Primary_Ignition_Failed : exception;

end Rocket_Motor;

package body Rocket_Motor is

   procedure Start is
   begin
      ...
   exception
      when Constraint_Error =>
         raise Primary_Ignition_Failed;
   end Start;

end Rocket_Motor;

with Rocket_Motor;
procedure Launch is
begin
   ...
   Rocket_Motor.Start;
   ...
exception
   when Primary_Ignition_Failed =>
      Fail_Safe; 
 
end Launch;

?
Are you just objecting to raising (e.g.) Constraint_Error?
If so, it would be reasonably easy to write an asis tool
to enforce this policy.


> How bare is the hardware?  If it's all
> *that* bare, it won't support I/O or exceptions either.

Bare = no OS.
Just the the language defined runtime + your program.