Re: [Boost-users] [boost-users][tuple] Tuple::get<0> as std::mem_fun_ref

29 Aug 2013


      Hi! Any updates on this? M.


2013/8/14 Miklós Tóth 
...
Hi!
I have a problem with std::mem_fun_ref and boost::tuple. Here is my code:
I have small LevelSetter class. It makes a level vector indexed by a
transform_iterator value.
template <typename LevelType>
class LevelSetter {
private:
    int nmb_of_elements;
public:
    LevelSetter(int nmb_of_elements_) : nmb_of_elements(nmb_of_elements_) {}
template <typename TrRange>
    std::vector<LevelType> set(TrRange range) {
        typedef typename TrRange::first_type TrIter;
        std::vector<LevelType> levels(nmb_of_elements);
        for (TrIter it = range.first; it != range.second; ++it) {
            levels[*it] = 0.0;
        }
        // much more complicated code
        return levels;
    }
};
Let's call it:
class MemFunRefTest
{
private:
typedef float Scalar;
    typedef boost::tuple Tuple;
    typedef std::vector<Tuple> Fwd;
    typedef Fwd::iterator FwdIter;
    typedef std::pair FwdRange;
Fwd elements;
public:
    MemFunRefTest() {
        elements.push_back(Tuple(0, 400.0));
        elements.push_back(Tuple(1, 120.0));
        elements.push_back(Tuple(2, 150.0));
    }
void fun() {
FwdRange element_range = std::make_pair(elements.begin(), elements.end());
LevelSetter<Scalar> setter(elements.size());
        setter.set(std::make_pair(
                       boost::make_transform_iterator(
                           element_range.first,
                           std::mem_fun_ref(&Tuple::get<0>)
                           ),
                       boost::make_transform_iterator(
                           element_range.second,
                           std::mem_fun_ref(&Tuple::get<0>)
                           )
                       )
                   );
    }
};
When I try to compile i get:
error: call of overloaded 'mem_fun_ref(<unresolved overloaded function type>)' is ambiguous
candidates are:
c:\mingw-4.6\bin\..\lib\gcc\i686-pc-mingw32\4.6.1\..\..\..\..\include\c++\4.6.1\bits\stl_function.h:697: std::mem_fun_ref_t<_Ret, _Tp> std::mem_fun_ref(_Ret (_Tp::*)()) [with _Ret = int&, _Tp = boost::tuples::cons >]
c:\mingw-4.6\bin\..\lib\gcc\i686-pc-mingw32\4.6.1\..\..\..\..\include\c++\4.6.1\bits\stl_function.h:702: std::const_mem_fun_ref_t<_Ret, _Tp> std::mem_fun_ref(_Ret (_Tp::*)()const) [with _Ret = const int&, _Tp = boost::tuples::cons >]
What am I missing?
Thanks, Miklos