List.h sort() Function

[hopestar]

I want to create a list of the following structure:

struct Element() {
int node;
int timestamp;
}

list<Element *> elementList;

Is there a way to use the .sort() function from the list.h class to sort elementList ONLY by the timestamp?? If not, are there any other suggestions for doing this in an easy manner? Thanks in advance for any help!!

[vinodp]

To work sort with list U need to define comparison operator <(less than)for ur struct or class.
Define that operator in ur struct. & just compare timestamp value there

Vinod

[Philip Nicoletti]

Here is an example. Some notes :

• if your compiler supports it, you should use #include <list> , not <list.h>
  
• the code below uses the predicate form of the sort() member function.
  Old version of Visual C++ do not support this (you can get an upgrade
  from dinkumware - but its not free).
  

#include <list>
#include <iostream>

struct Element
{
    int node;
    int timestamp;
};


struct sort_by_timestamp
{
	inline bool operator () (const Element * lhs , const Element * rhs) const
	{
		return lhs->timestamp < rhs->timestamp;
	}
};

int main()
{

    std::list<Element *> elementList;
    std::list<Element *>::iterator iter;

    Element *p;

    p = new Element;
    p->node      = 0;
    p->timestamp = 90;
    elementList.push_back(p);

    p = new Element;
    p->node      = 1;
    p->timestamp = 50;
    elementList.push_back(p);

    p = new Element;
    p->node      = 2;
    p->timestamp = 80;
    elementList.push_back(p);

    //--- print list before sort
    std::cout << "unsorted list" << std::endl;
    for(iter=elementList.begin(); iter!=elementList.end(); ++iter)
    std::cout << (*iter)->timestamp << " " << (*iter)->node << std::endl;

    //--- sort list by timestamp
    elementList.sort( sort_by_timestamp() );
  
    //--- print sorted list
    std::cout << std::endl << "sorted list by timestamp" << std::endl;
    for(iter=elementList.begin(); iter!=elementList.end(); ++iter)
    std::cout << (*iter)->timestamp << " " << (*iter)->node << std::endl;

    //--- cleanup
    for(iter=elementList.begin(); iter!=elementList.end(); ++iter)
    {
        delete *iter;
    }

    elementList.clear();
 
    return 0;
}