Exception Safe Guard

After reading Andrei Alexandrescu and Petru Marginean's
"Generic: Change the Way You Write Exception-Safe Code ?? Forever"
http://www.ddj.com/cpp/184403758

I borrow Boost.Function, which makes the implementation much simpler.

here goes the demo:

#include <boost/function.hpp>
#include <boost/bind.hpp>
#include <boost/noncopyable.hpp>

#include <iostream>
#include <ctime>
#include <cstdlib>

using namespace boost;

using namespace std;

struct Guard
     : private noncopyable
{
     Guard(function0<void> const& op)
         : op_(op), committed_(false) {}

     void Commit() throw()
     {
         committed_ = true;
     }

     ~Guard()
     {
         if (!committed_)
             op_();
     }

private:
     bool committed_;
     function0<void> op_;
};

struct Obj
{
     void Rollback() const {
         cout << "Committed, Now Rolling back" << endl;
     }
};

void MayThrow() throw(int)
{
     srand(time(0));
     if (int r = rand() % 2)
         throw r;
}

int main()
try
{
     Obj obj;
     Guard guard(bind(&Obj::Rollback, obj));

     // do the stuffs, which may throw
     MayThrow();

     guard.Commit();
}
catch (int i)
{
     cout << "Exception: i = " << i << endl;
}
catch (...)
{
     cout << "Unknown Exception" << endl;
}

Any suggestion is welcomed, including coding style.

--
Thanks
Barry