Question

I have a std::list<myclass*> and in my class I have myclass::operator<(myclass &other) defined.

I use the std::list.sort() function, but it does not change anything in that list. Maybe it just sorts the pointers?

How can I sort the actual items in that list?

Answer 1

You are sorting the pointer values, not the myclass values. You have to write your own predicate to compare pointers by dereference:

template <typename T> bool PComp(const T * const & a, const T * const & b)
{
   return *a < *b;
}

std::vector<Foo*> myvec;
std::list<Foo*> mylist;
std::sort(myvec.begin(), myvec.end(), PComp<Foo>);
mylist.sort(PComp<Foo>);

By the way, I think you cannot sort std::list with std::sort from <algorithm> because it is not random access. Use the member function sort instead as MerickOWA says. (But that’s generally less efficient than sorting a random-access container.) Alternatively, you can immediately store your objects in a sorted container like std::set<Foo*, PPred>, where PPred is the functor version of the predicate:

struct PPred {
  template <typename T> inline bool operator()(const T * a, const T * b) const
  { return *a < *b; }
};