Re: How to get nice with GNAT?

[brbarkstrom@gmail.com]

On Thursday, November 27, 2014 4:01:19 AM UTC-5, Dmitry A. Kazakov wrote:
> On Wed, 26 Nov 2014 14:38:29 -0800 (PST), brbarkstrom wrote:
> 
> > I think it may be sensible to think of exceptions as contingent events
> > that we couldn't include in the original design because
> > a) we aren't omniscient
> > [as a subset of that] a1) we're building complex mechanisms that have
> > unexpected interactions between the parts
> 
> ?
> 
> > b) the environment in which the program operates changes in unpredictable
> > ways
> > As a result, we are nearly certain to discover unexpected events only after
> > we put the system into operation.
> 
> No. Exceptions are *expected* events (system states), always.
> 
> An unexpected event is when a nuke falls down on the system box. Bugs are
> unexpected events.
> 
> Exception propagation is not a bug. It is a valid and anticipated system
> state. Compare it with 2x3 computed as 5 because addition was used instead
> of multiplication. This is also a bug, but there is nothing vicious in
> addition per se.
> 
> -- 
> Regards,
> Dmitry A. Kazakov


Sure, but often enough we add in exceptions after having to respond to an 
unexpected event.  The addition of the exception comes in maintenance, rather 
than as result of the design work.  Of course, sometimes we've had enough 
experience with previous errors to put the exception in as part of the design.

Thanks for the clarification.

Bruce B.