Sorting a vector of user defined type

[avimitrani]

Hi,

I am trying to apply the sort() algorithm on a vector of structs. I want the vector to be sorted according to one of the struct fields. I see two ways in which this could be done, and neither seems to work.

Here are the struct and the vector:

    struct item_calculation 
    {
        int item_num;
        float weight;
        float contribution;
        float prediction;
    };
 
               vector<item_calculation> found_items; 

I want the vector "found_items" to be sorted by the field "prediction".

The first way to do the task is defining a comparison function and sending it do sort() as a parameter:

    bool less_than( item_calculation a, item_calculation b ) {
        return a.prediction < b.prediction;
    };              
.
.
.
    sort(found_items.begin(), found_items.end(), less_than); 

This results with the errors: "error C3867: 'CCFEApp::less_than': function call missing argument list; use '&CCFEApp::less_than' to create a pointer to member."; "error C2780: 'void std::sort(_RanIt,_RanIt)' : expects 2 arguments - 3 provided"

when using "&CCFEApp::less_than" I get the error: "error C2914: 'std::sort' : cannot deduce template argument as function argument is ambiguous".

The second way to do the task is by overloading the "<" operator:

    bool operator<(item_calculation a, item_calculation b) {
        return a.prediction < b.prediction;
    }; 

gives: "error C2804: binary 'operator <' has too many parameters".

After changing to:

    bool operator<(item_calculation b) {
        return prediction < b.prediction;
    }; 

one gets: "error C2065: 'prediction' : undeclared identifier".

I would apreciate any help.

Thanks,
Avi.

P.S. I am working under Visual Studio 2005.

[D_C]

I used a list, but I can't imagine it's that different for vectors.
Edit - This is also STL code.

static bool fname(Person l, Person r) // Person::fname
{
  return (l.getFname() < r.getFname());
}
 
// list<Person> people;
// Later when I needed to sort I used
people.sort(Person::fname);