Question

there. I’ve searched my question around here but failed to find anything relevant.
This is the problem.
I have this code in the part of my program, doing kind of stupid sort by inserts.
I developed that in MSVS 2008 and it all worked fine, but when I tried to compile that with g++, it failed because of list::insert function below;

//...
pair<uint, double> NewElem(i, Prob.at(i));
bool inserted(false);
vector<pair<uint, double> >::const_iterator li = NewList.begin();
for ( vector<double>::const_iterator ji = BlocksMemory.begin() ; ji != BlocksMemory.end() ; ++ji)
{
    if (NewElem.second <= *ji)
        li += _SORT_BLOCK;
    else
        break;
}
for(;li != NewList.end() ; ++li)
{
    if (NewElem.second > li->second)
    {
        NewList.insert(li, NewElem );
        inserted = true;
        break;
    }
}

as one can see, li is const_iterator of NewList;
And NewElem has type pair with the same content type as NewList contents;

There you can see the response (unreadable):

main.cpp:447: error: no matching function for call to "std::vector<std::pair<unsigned int, double>, std::allocator<std::pair<unsigned int, double> > >::insert(__gnu_cxx::__normal_iterator<const std::pair<unsigned int, double>*, std::vector<std::pair<unsigned int, double>, std::allocator<std::pair<unsigned int, double> > > >&, std::pair<unsigned int, double>&)"

/usr/include/c++/4.4/bits/vector.tcc:106: note: candidates are: __gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> > std::vector<_Tp, _Alloc>::insert(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp = std::pair<unsigned int, double>, _Alloc = std::allocator<std::pair<unsigned int, double> >]

/usr/include/c++/4.4/bits/stl_vector.h:850: note: void std::vector<_Tp, _Alloc>::insert(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, size_t, const _Tp&) [with _Tp = std::pair<unsigned int, double>, _Alloc = std::allocator<std::pair<unsigned int, double> >]

What can be the reason? And what is the possible solution?

Answer 1

The signature of the insert member function that you are trying to use is probably:

iterator insert( iterator, const value_type& );

But the first argument that you are passing to the function is a const_iterator, that cannot be implicitly converted to a non const iterator. That code should not have worked on VS either.

The simple solution is that if you intend to modify the container you use a non-const iterator: define li as std::vector< std::pair<uint,double> >::iterator li = NewList.begin();