[boost] correct usage of bind (pls ignore last email)

Subject: [boost] correct usage of bind (pls ignore last email)
From: Sandeep Gupta (gupta.sandeep_at_[hidden])
Date: 2009-03-17 18:22:20

Hi,
 The code below tries to chain  function ft1 (argument is a pair) with
function buildPair (returns a pair).

template<typename X, typename Y>
std::pair<X, Y> buildPair(X x, Y y)
{
  std::pair<X,Y> apair(x,y);
  return apair;
}

int main()
{
  typedef boost::function<void (std::pair<int,int>)> FuncType1_t;
  std::vector<std::pair<int,int> > myvec;
  FuncType1_t ft1 = bind(&std::vector<std::pair<int,int> >
::push_back, &myvec, _1);

  typedef boost::function<void(std::pair<int,int>)> FuncType2_t;
  FuncType2_t ft2 =  bind(ft1, bind(buildPair<int,int>,_1,_2));
               //compile fails

  return 0;
}

This fails. The problem however vanished if I replace the declaration
"FuncType3 ft2..."  with
  bind(ft1, bind(buildPair<int,int>,_1,_2))(3,5);

So my question is what is correct type of  bind(ft1,
bind(buildPair<int,int>,_1,_2));

Thanks
sandeep