Re: derive from std::set, const_iterator does not work

From:

Abhishek Padmanabh <abhishek.padmanabh@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sat, 7 Jun 2008 23:16:37 -0700 (PDT)

Message-ID:

<ec175ed4-c4e0-4ea2-a814-6da0778f17f3@u12g2000prd.googlegroups.com>

On Jun 8, 8:27 am, Markus Dehmann <markus.dehm...@gmail.com> wrote:

I want to derive from std::set, like shown below. But when I try to
declare an iterator over the contained elements I get an error, see
the twp uncommented lines:

#include <set>
template<class T>
class MySet : public std::set<T>{
public:
  MySet() : std::set<T>() {}
  void foo(){
    // const_iterator it; // error: `const_iterator' undeclared (first=

use this
function)
    // std::set<T>::const_iterator it; // error: expected `;' before
"it"
  }

};

I thought const_iterator should be a member of this class (since I am
deriving from std::set). What am I doing wrong?

Not getting into why you want to derive from a standard container,
here's how you can make it work:

#include <set>

template<class T>
class MySet : public std::set<T>{
public:
  MySet() : std::set<T>() {}
  void foo(){
    //either create typedefs to use iterator/const_iterator directly
    typedef typename std::set<T>::const_iterator const_iterator;
    typedef typename std::set<T>::iterator iterator;
    const_iterator it;
    //or use fully qualified names but will need typename
    typename std::set<T>::const_iterator it2;
  }
};

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