1

I am trying to resort a STL set by creating a new set and creating a custom sort function with a custom sort function , please refer to my previous qn on how its done

This is a dumbed down version of the code sample which works in Quincy 2005(G++ compiler) but does not work in Microsoft studios 2010

#include <iostream>
#include <string>
#include <fstream>
#include <set>
#include <cmath>


using namespace std;

class Point2D
{
 public:

           int getX() const;
           int getY() const;

           void setX(int);
           void setY(int);


          bool operator < ( const Point2D& x2) const
          {
            if ( x != x2.x)
            {
            return x < x2.x;
            }
            if ( y != x2.y)
            {
              return y < x2.y;
            }
          };

 protected:

             int x;
             int y;


};

struct SortByYX
{
  bool operator ()(const Point2D& ptd1, const Point2D& ptd2) const
  {
    if ( ptd1.getY() != ptd2.getY())
    {
        return ptd1.getY() < ptd2.getY();
    }
  if ( ptd1.getX() != ptd2.getX() )
    {
        return ptd1.getX() < ptd2.getX();
    }

    return false;
  }
};




int main()
{
    set<Point2D> p2d_set;

    Point2D p2d;

    p2d.setX(1);
    p2d.setY(3);

    p2d_set.insert(p2d);

    p2d.setX(3);
    p2d.setY(2);

    p2d_set.insert(p2d);

    set<Point2D>::iterator p2 = p2d_set.begin();

   while ( p2 != p2d_set.end() )
   { 
     cout<<p2->getX()
         <<" "
         <<p2->getY()
         <<endl;
     p2++;
   }


  set<Point2D, SortByYX> p2d_set2(p2d_set.begin(), p2d_set.end());

  set<Point2D>::iterator p22 = p2d_set2.begin();

   cout<<endl
       <<endl;

   while ( p22 != p2d_set2.end() )
   { 
     cout<<p22->getX()
         <<" "
         <<p22->getY()
         <<endl;
     p22++;
   }






}



int Point2D::getX() const
{
   return x;
}

int Point2D::getY() const
{
   return y;
}
void Point2D::setX(int x1)
{
   x = x1;
}

void Point2D::setY(int y1)
{
 y = y1;  ;
}

I am getting the following errors when it is compiled in MS Studio 2010 , it compiles fine in Quincy 2005

error C2440: 'initializing' : cannot convert from 'std::_Tree_const_iterator<_Mytree>' to 'std::_Tree_const_iterator<_Mytree>'

Error C2678: binary '!=' : no operator found which takes a left-hand operand of type 'std::_Tree_const_iterator<_Mytree>' (or there is no acceptable conversion

system_error(425): could be 'bool std::operator !=(const std::error_code &,const std::error_condition &)'

I am sure it has something to do with the custom sort function as the problem arises when i attempt to create a new set using SortByYX as my comparison function

struct SortByYX
{
  bool operator ()(const Point2D& ptd1, const Point2D& ptd2) const
  {
    if ( ptd1.getY() != ptd2.getY())
    {
        return ptd1.getY() < ptd2.getY();
    }
  if ( ptd1.getX() != ptd2.getX() )
    {
        return ptd1.getX() < ptd2.getX();
    }

    return false;
  }
};

I need help

1) understanding why does this sample of code work in Qunicy2005 but not in MS Studio 2010

2) How do i get the sample of code working in MS Studio 2010 also

4

1 回答 1

2

您在这里使用了错误类型的迭代器：

set<Point2D>::iterator p22 = p2d_set2.begin();

你需要

set<Point2D, SortByYX>::iterator p22 = p2d_set2.begin();

请记住，set<Point2D>和set<Point2D, SortByYX>是不同的类型，它们iterator的 s 也是如此。

于 2013-11-14T16:22:03.863 回答