Having trouble printing out values in a map of maps

[freddy92]

Hi guys, as the title states, I'm having some trouble going through a map of maps and printing out all of the values. Here is my declaration of the map:

map<T, map<T, int> > adjList;

And here is my Display function:

template<typename T>
void Graph<T>::display() const
{
	map<T, map<T, int> >::iterator iter;
	for (iter = adjList.begin(); iter != adjList.end(); ++iter)
	{
		cout << iter->first << endl;
		map<T, int>::iterator pos;
		for (pos = adjList[iter->first].begin(); pos != adjList[iter->first].end(); ++pos) 
		{
			cout << pos->first << "  " << pos->second << endl;
		}
	}
}

When I try to compile this, I get the follow error:

error C2679: binary '=' : no operator found which takes a right-hand operand of type 
'std::_Tree_const_iterator<_Mytree>' (or there is no acceptable conversion)

I'm pretty new to using iterators for this type of thing, and completely new to maps as well. Any help would be appreciated.

[johnbob]

You could try replacing adjList[iter->first] by iter->second.

I don't know if there's any difference.

[Peter87]

The function is marked as const so you probably have to use const_iterator.

map<T, map<T, int> >::const_iterator iter;

map<T, int>::const_iterator pos;

[freddy92]

Yes, the problem was using a non-const iterator in a const function. Thanks.