Re: Exceptions as objects (was Re: What is wrong with OO ?)

[Kyzivat@Kyzivat.ultranet.com (Paul Kyzivat)]

piercarl@sabi.demon.co.uk (Piercarlo Grandi) wrote:

[snip a long and interesting explanation of exception handling]

I found the discussion very interesting. In a theoretical way I agree
with you. However I think in a practical sense it misses the point to
an extent:

For code to be readable, it is useful to have the exception handling
easily and clearly lexically scoped with the code that it applies to.
What you suggest is really very little different than what existed in
various libraries prior to the introduction of compiler supported
exception handling. I remember it in Fortran - it did a nice job of
adding to the confusion of all those gotos.

You are right that this really has more to do with how to suport a new
form of non-local control transfer than it does exceptions. But
usually non-local control transfer is required for exception handling
because the function otherwise has no return arguments that can be
used to express what happened. And, while TRY is ugly and clumsy in
some cases, it does allow the normal flow of control to be segregated
from the abnormal flow of control while still making it clear how they
are related.

I agree with you that classes as exceptions is in a way a kludge. But
they do more than pass arguments to a handler. They also server as a
hierarchical classification system for exceptions. Using classes for
this is a matter of economy of language concepts. (Perhaps we can call
it reuse of a language concept.)

	Paul Kyzivat