List.Sort(cmp_fnc) term does not evaluate to a function taking 2 arguments?

[Shaitan00]

I am trying to customize my sorting of a LIST using a compare_function, but for some odd reason it keeps giving me the following error:
error C2064: term does not evaluate to a function taking 2 arguments

Specifically, I have list created within class B which needs to be sorted, the list contains elements of type A* as shown below:

Class B code:
[Code]
B::B()
{
list<A*> AList;

AList.push_back(new A(ID_1, CODE_1));
AList.push_back(new A(ID_2, CODE_2));

AtList.sort(&B::compareID);
}

bool B::compareID(A* first, A* second)
{
return true; // test for now
}
[Code]

Just for completness the following is the code for Class A:
[Code]
Class A
{
long ID;
string sCode;
A(_ID, _sCode) : ID(_ID), sCode(_sCode) {};
}
[Code]

So, pretty much I just want to sort AList by ID, but for some odd reason this generates:
error C2064: term does not evaluate to a function taking 2 arguments

Also, in the future I am going to want to create a compareCode() function to also compare by code ... thought if one way works so will the other ...

Any clues, hints, or help would be greatly appreciated.
Thanks,

[helios]

Make compareID() a regular function instead of a method.

[kempofighter]

This is what mem_fun is for as well.
http://www.cplusplus.com/reference/std/functional/mem_fun/

Also, I think that boost::bind does something similar. If you are able to use boost, I'd recommend looking into that.

I'm not sure what the best answer is from a design standpoint to be honest. There are quite a few ways to solve your problem. Helios' suggestion is also fine. By regular function I think he means global (define it outside of class). Another possibility is to make it a static function of the class. Another possibility would be to declare a functor class and pass a functor to list::sort. Personally, I think it is better if the function is a member of A since A objects are being sorted. That just makes more sense to me.

Keep in mind that for sorting the predicate, whichever way you do it, must be a pure function. Google "pure function" if you don't know what that means.

[helios]

If you want to get fancy, you could make it a static method of B. Static members are just globals in a different namespace, so it's basically the same. Personally, I would go for the simpler global function.