Re: STL set with object pointer list

From:

Ondra Holub <ondra.holub@post.cz>

Newsgroups:

comp.lang.c++

Date:

Thu, 16 Aug 2007 03:55:09 -0700

Message-ID:

<1187261709.727538.216040@d55g2000hsg.googlegroups.com>

On 16 Srp, 12:03, Ami <ver_amit...@yahoo.com> wrote:

Hi All,
  I am trying to create a sorted list of class objects using set<
myclass* >. My class has one member variable which i used as
comparison criteria. I have over loaded the "<" operator also so that
objects should be inserted in sorted order but problem which i face is
that this overloaded function is not called at all. Please can anybody
help me to make it working.
code snippet is as follows:

//class
class myclass
{
public:
   myclass(int data);
    bool operator <(const myclass& otherclass) const;
    int getdata(){return m_data;}
private:
   int m_data;

}

//constructor
myclass::myclass(int data)
{
  m_data=data;

}

//operator overloaded for comparision
bool myclass::operator <(const myclass& otherclass) const
{
   retrun (getdata() < otherclass.getdata());

}

//class set
set<myclass* > myclassset;

void main()
{
    myclass *obj1 = new myclass(1);
    myclass *obj2 = new myclass(2);

    myclassset.insert(obj1);
    myclassset.insert(obj2);

      .......................
      .....................

}

Thanks and Regards

You have to supply compare class as second parameter of set template.
because currently only pointers are compared (not instances, for which
you have operator<).

struct Compare
{
    bool operator()(myclass* obj1, myclass* obj2) const
    {
        // Here write your own comparison
        return *obj1 < *obj2;
    }
};

std::set<myclass*, Compare> MySet;