[boost] Exception Visitor

From: Jeremy Day (jeremy.day_at_[hidden])
Date: 2006-07-18 13:06:34

All,

A message a few days ago, along with my current reading of the book 'C++
Template Metaprogramming', piqued my interest in the idea of an "exception
visitor".  I put together a little something, and I'm wondering if people
might be interested in my (rather poor, at the moment) code.

Problem:

When using exceptions it is very easy to end up with code that looks
something like this:

try
  {
  //Some code that might throw exceptions.
  }
catch(std::logic_error&)
  {
  //Handle the exception.
  }
catch(std::exception&)
  {
  //Handle exception.
  }
catch(...)
  {
  //Handle everything else
  }

With my code you can transform the above into something along these lines:

struct my_exception_handler
    {
    typedef boost::mpl::vector<std::logic_error, std::exception> exceptions;

    void operator()(std::exception& oError)
        {
        std::cout << "my_exception_handler::operator()(std::exception&)" <<
std::endl;
        }

    void operator()(std::logic_error& oError)
        {
        std::cout << "my_exception_handler::operator()(std::logic_error&)"
<< std::endl;
        }

    void operator()(void)
        {
        std::cout << "my_exception_handler::operator()(void)" << std::endl;
        }
    };

//Application code.

try
  {
  //Some code that might throw exceptions, such as:
  throw std::logic_error("A sample logic error.");
  }
catch(...)
  {
  //Magic happens here.
  catcher(my_exception_handler()); //This prints out
"my_exception_handler::operator()(std::logic_error&)"
  }

If anyone is interested I will post what I have for critique (I'm a relative
newbie with MPL, so I will likely need a lot of help).  I look forward to
any and all comments.

Jeremy