Problem with Boost bidirectionnal iterator not writable

I try to make bidirectionnal iterators with Boost Iterator. I have implemented some functions as suggested in the documentation here.

I have a parent class where the funct开发者_开发百科ions to implement are declared pure virtual (I need polymorphic iterators). For the moment, I have one inherited class where the functions are implemented. Moreover, I use boost::bidirectional_traversal_tag.

The dereference() function is implemented as follows in the inherited class:

template <typename T>
T& ImageIterator_NotPlanar<T>::dereference() const {
  return *((T*)buffer);
}

to read values as the following example, it works perfectly:

for (; !iter.isEndReached(); ++iter)
  cout << "ITERATOR INC: " << *iter << endl;

(where isEndReached() is a personal function). The problem is that the following code doesn't works:

*iter = 3;

g++ returns the following error:

lvalue required as left operand of assignment

What is wrong ?

Thanks

We need to see exactly where the error is generated. Also, we have to assume you have the proper non-const version

Could it be you need to have

template <typename T>
T& ImageIterator_NotPlanar<T>::dereference() {
  return *((T*)buffer);
}

template <typename T>
T const& ImageIterator_NotPlanar<T>::dereference() const {
  return *((T*)buffer);
}