STL list <unsigned short> and ostream

[shrinath]

Hi
I have a following class:
/////////////////Data.h
class Data {
public:
...
friend ostream& operator<< (ostream& out, const Data& rData);
...
private:
list <unsigned short> seq;
...
}

and its implementation as
/////////////////Data.cpp
....
ostream& operator<< (ostream& out, const Data& rData) {
list<unsigned short>::iterator itr;
for (itr = rData.seq.begin (); itr != rData.seq.end (); itr++) {
out << *itr;
}
return out;
}
...

I am using g++ (GCC) 4.2.3 (Ubuntu 4.2.3-2ubuntu7 x86_64-linux-gnu)

It gives me the following error on compile:

$>g++ testDriveriData.cpp Data.cpp
Data.cpp: In function ‘std::ostream& operator<<(std::ostream&, const Data&)’:
Data.cpp:51: error: no match for ‘operator=’ in ‘itr = rData->Data::seq.std::list<_Tp, _Alloc>::begin [with _Tp = short unsigned int, _Alloc = std::allocator<short unsigned int>]()’
/usr/include/c++/4.2/bits/stl_list.h:113: note: candidates are: std::_List_iterator<short unsigned int>& std::_List_iterator<short unsigned int>::operator=(const std::_List_iterator<short unsigned int>&)

Any clue?
Similar code in other program works fine.

Thanks.
-sn

[exception]

You are requesting a non-const iterator from a const reference. This doesn't work. An improved solution:

class Data
{
  public:
    ...
    std::ostream& print(std::ostream& os) const
    { // not really inlined, just for brevity
      std::copy(seq.begin(), seq.end(), std::ostream_iterator<unsigned short>(os, " "));
      return os;
    }
    ...
};
...
std::ostream& operator<< (std::ostream& out, const Data& rData)
{
  return rData.print(out);
}

This wil print a " " between each number, can be substituted by "\n" or nothing at all if you want.

[shrinath]

Hi exception,

It (ostream) now works.
Also changing the iterator in the original code (from iterator to the const_iterator) works.
I got that hint from your answer.

Thank you for the correct reply.

-sn