Problem with using "pEdge==NULL"

[Jeffrey Holle <jeffreyholle at bellsouth dot net>]

Using gcc/g++ version 4.1.2

I'm creating an application that attempted to employ the statement:
  if(m_future.getEdges().second!=NULL)
    the getEdges method is defined as:

      typedef std::pair<const DataEdge*,const DataEdge*> Edges;
      Edges getEdges(void) const {return 
std::make_pair(m_pEdge1,m_pEdge2);}

This statement always considered the second pair element as not NULL.

I've fixed my problem by creating another method:
  bool isIntersection(void) const { return (m_pEdge2==NULL) ? true : 
false;}

Then "if(!m_future.isIntersection())" works as expected.

It really seems like either should have worked, but only the second did.

I'd like an explanation.