[Mingw-users] stl/container/iterator problem

[Nicolas W. <nic...@gm...>]

Hi!
There seems to be a problem with the stl list iterator...I'm writing a small
polygon(2d) editor. I wrote the two classes Vector2d and Polygon2d and
Poly2d has operator[] overloaded, it returns a Vector2d reference. Vector2d has
the methods getX() and getY(). PolyIterator is typedef'd as
list<Polygon2d>::iterator. Now I have the following piece of code:

  //m_polyList is list<Polygon2d>
  PolyIterator listEnd = m_polyList.end();
  PolyIterator e;
  for(e = m_polyList.begin(); e != listEnd; ++e)
  {
    int vertexCount = e->getVertexCount();
    if(vertexCount <= 0)
      continue;

    //draw poly

    MoveToEx(hDc, (int)(*e)[0].getX(), (int)(*e)[0].getY(), NULL);

    for(int i = 1; i < vertexCount; ++i)
    {
      LineTo(hDc, (int)(*e)[i].getX(), (int)(*e)[i].getY());
    }

    LineTo(hDc, (int)(*e)[0].getX(), (int)(*e)[0].getY());
  } //end for

This does not work as expected (e is a Polygon2d iterator, so *e is a
Polygon2d and (*e)[0].getX() should call operator[] on the Poly and getX() on the
returned Vector2d). It compiles, but the output looks very strange...it does
work, however, if I save *e in a Polygon2d reference and use that, like so:

  for(e = m_polyList.begin(); e != listEnd; ++e)
  {
    int vertexCount = e->getVertexCount();
    Polygon2d& poly = *e;
    if(vertexCount <= 0)
      continue;

    //draw poly

    MoveToEx(hDc, (int)poly[0].getX(), (int)poly[0].getY(), NULL);

    for(int i = 1; i < vertexCount; ++i)
    {
      LineTo(hDc, (int)poly[i].getX(), (int)poly[i].getY());
    }

    LineTo(hDc, (int)poly[0].getX(), (int)poly[0].getY());
  } //end for

Any ideas why this is the case?
TIA,
Nico

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