[boost] Sorting list < shared_ptr < foo > > using std::list::sort()

From: HEATH DAVIS (1heathdavis_at_[hidden])
Date: 2003-04-24 01:21:36

I have experienced some difficulty with sorting lists of type:

list < shared_ptr < foo > >

Here is the expected (sorted) program output:

424238335
596516649
719885386
846930886
1189641421
1649760492
1681692777
1714636915
1804289383
1957747793

Instead, I end up with:

1804289383
846930886
1681692777
1714636915
1957747793
424238335
719885386
1649760492
596516649
1189641421

Below is the code in question:

////////////////////////////////////////////////

#include <iostream>
#include <list>
using namespace std;

#include <boost/shared_ptr.hpp>
using namespace boost;

////////////////////////////////////////////////

class my_class
{
public:
int m_val;
public:
my_class();

bool operator<(const my_class&);
void Display();
};

////////////////////////////////////////////////

my_class::my_class()
{
m_val = rand();
}

bool my_class::operator<(const my_class& arg)
{
return m_val < arg.m_val;
}

void my_class::Display()
{
cout << m_val << "\n";
}

////////////////////////////////////////////////

int main( int argc, char **argv )
{
// list < my_class > my_list;
// list < my_class >::iterator my_iter;

list < shared_ptr < my_class > > my_list;
list < shared_ptr < my_class > >::iterator my_iter;

//populate my_list
for (int x=0; x<10; x++)
{
// my_class tmp_obj;

shared_ptr < my_class > tmp_obj;
tmp_obj.reset(new my_class);

my_list.push_back(tmp_obj);
}

//sort the list
my_list.sort();

//display contents of my_list
my_iter = my_list.begin();
while (my_iter != my_list.end())
{
// (*my_iter).Display();

(*my_iter)->Display();

++my_iter;
}

return 0;
}

////////////////////////////////////////////////

Thanks in advance for any help you may render...

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