Question

I have the following typedef’s in my code:

typedef unsigned long int ulint;
typedef std::map<ulint, particle> mapType;
typedef std::vector< std::vector<mapType> > mapGridType;

particle is a custom class with no default constructor.

VS2008 gives me an error in this code:

std::set<ulint> gridOM::ids(int filter)
{
    std::set<ulint> result;
    ulint curId;
    for ( int i = 0; i < _dimx; ++i ) {
        for ( int j = 0; j < _dimy; ++j ) {
            // next line is reported to be erroneous
            for ( mapType::iterator cur = objectMap[i][j].begin(); cur != objectMap[i][j].end(); ++cur )
            {
                curId = (*cur).first;
                if ( (isStatic(curId) && filter != 2) || (!isStatic(curId) && filter != 1) )
                {
                    result.insert(curId);
                }
            }
        }
    }
    return result;
}

objectMap is an object of mapGridType. The error reads:

error C2512: 'gridOM::particle::particle' : no appropriate default constructor available
while compiling class template member function 'gridOM::particle &std::map<_Kty,_Ty>::operator [](const unsigned long &)'  
        with  
        [  
            _Kty=ulint,  
            _Ty=gridOM::particle  
        ]  
        .\gridOM.cpp(114) : see reference to class template   instantiation 'std::map<_Kty,_Ty>'   being compiled  
        with  
        [  
            _Kty=ulint,  
            _Ty=gridOM::particle  
        ]  

Correct me if I’m wrong, but the above code should not be making calls to map::operator[] at all. The first operator[] call is made to vector< vector<mapType> > and returns a vector<mapType>, the second is made to vector<mapType> and returns a mapType aka a map<ulint, particle>, and I only call begin() and end on that map. So why do I get an error trying to compile the operator[] for map?

Answer 1

Case closed. It turns out that I did in fact make the coding mistake of writing a call to operator[], but it was hundreds of lines further down in the source file from where the error was reported. Apparently VS just pointed me to the first usage of a variable of mapType instead of the actual point where it tried to instantiate the method.