erase-remove idiom problems for vector in a class

Question

I am using class1 that contains a few governing variables and a vector of another class, class2. I would like to be able to flag various elements of the vector of class2 (using boolean variable 'delete_me') and then run the erase-remove idiom to eliminate those elements from the vector. I have found some examples of this on the web, but these are for simpler data structures than what I am using.

I am getting a type conversion error when I compile (using g++ v4.7.3).

Class2:

class Interval_structure {
   //class uses default destructor
   public:
      float x1, x2, y1, y2;
      float A; 
      float B; 
      float delta_x; 
      bool delete_me;
etc...

Class 1:

class CMR_Spline {
   //class uses default destructor
   public:
      vector< Interval_structure > Interval;
      int some_ints; 
      float some_floats;

  bool IsMarkedToDelete( Interval_structure& o )
  {
      return o.delete_me;
  }

  void prune_Intervals() {
  //intervals that have been slated for deletion are removed using the remove-erase idiom
     Interval.erase( remove_if(Interval.begin(), Interval.end(), IsMarkedToDelete ), Interval.end() );

  }

When I compile I get the following error, cited for the single line in the prune_Intervals routine using erase+remove_if:

error: cannot convert CMR_Spline::IsMarkedToDelete' from typebool (CMR_Spline::)(Interval_structure&) ' to type `bool (CMR_Spline::*)(Interval_structure&)'

I'm a little confused as to how I should write the IsMarkedToDelete function and prune_Intervals routine to correctly reflect the pointer that is used by remove-if to traverse the vector and evaluate IsMarkedToDelete.

How do I do this correctly using erase+remove_if, or if not that way please suggest an alternative approach. I am stumped and hindered by my limited programming experience. Thanks!

Answer 1

Make the function static:

static bool IsMarkedToDelete( Interval_structure& o )
{
    return o.delete_me;
}