Re: new revision ada

[Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>]

Brian May <bam@snoopy.apana.org.au> wrote:
: 
: Personally I have very happy with Ada95 the way it is, the only
: exception being exception handling which tends to look restrictive now
: compared with, say Java exceptions (as functions declare what
: exceptions they can raise, and can pass more information in the
: exception instead of just a string).

If you want to handle an exceptional situation with something
more "powerful" than an exception handler, then you might actually
be referring to a different notion of exception.
If it is more like backtracing, why not use a programming construct
that (I think) is closer in spirit to backtracing?  If the exception
is not what is traditionally called an exception but rather a special
program state that is special rather than exceptional in the Ada(?)
sense, an exception handler might be at the wrong level of
abstraction. Just the same name for two different things.

Ada has facilities to implement "trying-out programming". If one
(logical) thread of control fails, and it is important to
collect information about why it failed and in what program
state, than save the relevant pieces of the program state
using the executable statements of a local exception
handler for example.
You can store the information somewhere for lookup, and
use Ada's exceptions, or task communication, or plain
returned values to inform the caller of the failure or
success. The caller can use this information to retrieve
what has been stored for lookup.