Re: [Boost-users] [Container] ptr_set with user define compare function

22 May 2009


      AMDG

梁绍池 wrote:
...
I've defined a function object as below:
struct BaseAddrLess : public std::binary_function<Base, Base, bool>  {
        result_type operator() (const first_argument_type& lhs, const
second_argument_type& rhs) const  {
              return &lhs < &rhs;
        }
  };
and use as a compare function in ptr_set like this:
   ptr_set<Base, BaseAddrLess> bset;
when the class Base is a abstract class the vc9 compiler will complain
  use of undefined type 'boost::result_of<F>'
What causes this problem? How to solve it?
Works for me.
Do you have a minimal test case that fails?
What version of Boost are you using?

#include <functional>
#include <boost/ptr_container/ptr_set.hpp>

struct Base {
virtual ~Base() = 0;
};

Base::~Base() {}

struct Derived : Base {};

struct BaseAddrLess : public std::binary_function<Base, Base, bool> {
result_type operator() (
const first_argument_type& lhs,
const second_argument_type& rhs) const {
return &lhs < &rhs;
}
};

int main() {
boost::ptr_set<Base, BaseAddrLess> bset;
bset.insert(new Derived());
}

In Christ,
Steven Watanabe