Re: [Boost-users] Problem using enable_if with gcc 3.4.4

3 Dec 2009

      On Thu, 3 Dec 2009, gao_bolin@voila.fr wrote:
...
Hi,
I am having some trouble using enable_if with gcc 3.4.4 (code below). Basically it is working as expected with functions ("bar"), but using it on member functions of a class ("Foo"), I am getting the error that this member function cannot be overloaded.
Visual 2008 and gcc4 seem to be ok with it though.
Any explanation and work around appreciated.
B.
--
#include <iostream>
#include <boost/type_traits.hpp>
#include <boost/utility/enable_if.hpp>
// This won't compile with gcc 3.4.4
class Foo
{
public:
 template < typename T >
 typename boost::enable_if<boost::is_same<T, int>, T>::type
 bar(int x)
 {
   std::cout << "A" << std::endl;
   return x;
 }
template < typename T >
 typename boost::disable_if<boost::is_same<T, int>, T>::type
 bar(int x)
 {
   std::cout << "B" << std::endl;
   return x;
 }
};
Try making the enable_if a parameter of the member function:

class Foo
{
public:
  template < typename T >
  int bar(
    int x,
    typename boost::enable_if<boost::is_same<T, int>, T>::type* = 0)
  {
    std::cout << "A" << std::endl;
    return x;
  }

  // and the same for the second version.
};

There is more information on these workarounds in section 3.4 of 
<URL:http://www.boost.org/doc/libs/1_41_0/libs/utility/enable_if.html>.

-- Jeremiah Willcock