iterator (adaptor) mysteries

"albrecht.fritzsche" <>
3 Oct 2006 20:41:23 -0400
In the quest for the simplest iterator adaptor possible I came
up with the idea of simply inheriting from the iterator I'd
like to adapt to, iw with code a la

#include <iostream>
#include <vector>
#include <iterator>

template<typename Iter>
class IteratorAdaptor : public Iter {
     IteratorAdaptor(const Iter& it) : it_(it) {}
     typename Iter::value_type operator*() { return *it_; }
     Iter it_;

using namespace std;

int main() {
   vector<int> array;
   for (size_t i=0; i<10; ++i)

   IteratorAdaptor<vector<int>::const_iterator> it(array.begin());
   IteratorAdaptor<vector<int>::const_iterator> end(array.end());
   cout << *it << endl;
   cout << *it << endl;
   for (; it != end; ++it)
     cout << *it << endl;

   return 0;

While this compiles on Vis C++ and on Dinkumware Exam (there even
with the EDG/C++ combination), I do get compile errors on Comeau

   "ComeauTest.c", line 6: error: not a class or struct name
   class IteratorAdaptor : public Iter
           detected during instantiation of class
           "IteratorAdaptor<Iter> [with Iter=const int *]" at line 24

On Vis C++ I do get strange runtime errors in some internal validation
checks in the _Vector_const_iterator::operator++()
    _SCL_SECURE_VALIDATE(this->_Mycont != NULL);

So, my question is - what it wrong with inheriting from an iterator
and then using this inherited class as an iterator?

Thanks for any help - I still have no idea where I have left
Standard C++.


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