Hi! Hmm, I was wrong in my subject. The question is regarding lambda, not mpl. So here again: Frank Birbacher wrote:

Hi!

I want to create a container of pointers to objects in a range (first,last(. I tried to use mpl, but have been without success. I understand, that the lambda "&_1" cannot specify its concrete return type, so I added ret<T>(...). But the resulting lambda is rejected by the make_transform_iterator function. I'm using boost 1.33.0 on gcc 4.0.2

//****** CODE BEGIN ****** #include <vector> #include <iterator> #include <boost/iterator/transform_iterator.hpp> #include <boost/lambda/lambda.hpp>

template<typename Iterator> void foo(Iterator first, Iterator last) { using boost::make_transform_iterator; using namespace boost::lambda;

typedef typename std::iterator_traits<Iterator>::pointer Pointer; std::vector<Pointer> objectPointers( make_transform_iterator(first, ret<Pointer>(&_1)), make_transform_iterator(last, ret<Pointer>(&_1)) ); // ... }

int main() { std::vector<int> v; //instantiate template: foo(v.begin(), v.end()); } //***** CODE END ******

// ** ERROR on GCC 4.0.2: ** /mnt/daten/develop/boost/boost/iterator/transform_iterator.hpp:43: Fehler: kein Typ namens »result_type« in »class boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::explicit_return_type_action<int*>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::other_action<boost::lambda::addressof_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1>

...

, boost::tuples::null_type, boost::tuples::null_type,

boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > >, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > >«

The error says it cannot find the type "result_type" in "class ....". What is wrong here?

Frank