Re: Assertion vs Exception Handling
* Chris Gordon-Smith:
James Kanze <james.kanze@gmail.com> wrote:
Whether exception handling or assertions are more appropriate
depends on the type of error and the application domain. And
possibly other considerations as well.
I would be interested to know whether there are any guidelines on this.
Sure. That's almost a given. But we're not a point yet where there's even any
consensus about the simplest things.
Consider the C++ standard library's exception hierarchy. I haven't heard about
anyone who use those exception types as their names indicate. Yet very good
brains were involved in forming the standard library.
Consider a language like Python where not only assertions are exceptions, but
some exceptions are used to signal success, like, hey, we exhausted an iterator
as expected, and there are even exceptions called ...Warning. :-)
Personally I think exceptions, as they're commonly expressed in most of today's
languages, are at a too low level of abstraction, sort of like goto.
I like the Eiffel approach to exception handling where exceptions always
indicate failure and the syntax makes it clear what you can do when an exception
occurs: achieve the goal in some other way (e.g. by simple retrying), or fail in
turn. I think this could be particularly clean in C++ where most cleanup can be
achieved via RAII, thus removing that aspect from exception handling. And I once
started a few threads over in [comp.std.c++] suggesting such higher level
syntax, including a few formal definitions, but all that came out of that was
that Dave Harris (I think it was) showed me -- and other readers -- how the
template pattern can express the basic Eiffel exception handling notion.
Cheers,
- Alf