Re: [boost] Exception Visitor

From: Jeremy Day (jeremy.day_at_[hidden])
Date: 2006-07-27 13:25:02

On 7/27/06, Oleg Abrosimov <beholder_at_[hidden]> wrote:

> one further improvement I see is to define simple macros to eliminate
> some details from client code. something like this would be appropriate:
>
> try {
>      throw std::logic_error("testing");
> } BOOST_CATCH(my_exception_handler());
>
> and
>
> try {
>      throw std::logic_error("testing");
> } BOOST_CATCH_EX(exceptions, my_exception_handler());

Good suggestions.  Done and done.

and of course, I agree with David Abrahams that exceptions typelist
> should be sorted to handle most derived first. boost::is_base_of<Base,
> Derived> from type_traits library can be used to achieve it.

Also a good suggestion.  Until last night I wasn't sure exactly how to
handle this, but I figured it out.

One more idea to improve maintainability of client code:
>
> class my_exceptions_handler
> {
>      BOOST_DEFINE_EXCEPTION_HANDLER_FIRST(exception_type,
> exception_variable, 1)
>      {
>          //code here
>      }
>      BOOST_DEFINE_EXCEPTION_HANDLER(exception_type2, exception_variable,
> 1, 2)
>      {
>          //code here
>      }
>      BOOST_DEFINE_EXCEPTION_HANDLER(exception_type2, exception_variable,
> 2, 3)
>      {
>          //code here
>      }
>      BOOST_DEFINE_EXCEPTION_HANDLER_LAST(exception_type,
> exception_variable, 3)
>      {
>          //code here
>      }
> };
>
> These macros automatically define exceptions list eliminating last piece
> of code duplication. numbers are used to decorate typelist' name that is
> already defined.

I'm not sure that I understand the need for the _FIRST and _LAST versions of
the BOOST_DEFINE_EXCEPTION_HANDLER macro.  I also don't understand why I
need to decorate the typelist's name.  If you have some pseudocode in mind
for the definitions of BOOST_DEFINE_EXCEPTION_HANDER_FIRST,
BOOST_DEFINE_EXCEPTION_HANDER, and BOOST_DEFINE_EXCEPTION_HANDER_LAST I'd be
happy to look into this.

As it stands now there is a new version of Boost Catcher in the vault.  I
added the BOOST_CATCH macros and the exception sorting.  Comments are
welcome and encouraged.

Jeremy