I’m writing a C++ program for a 2D RPG game, using the SDL2 libraries. I have a class named Entity that has a property named worldY:

class Entity 
{
public:
        ...
    // coordinate mondo: la mappa del mondo
    int worldX = 0, worldY = 0;
}

In another class GamePanel I declare one of its properties:

std::list<Entity> entityList;
std::vector<Entity> npc;

The NPC vector is filled with instances of the:

class NPC_OldMan : public Entity

in this way:

for (int i = 0; i < npc.size(); i++)
{
    if (!npc.at(i).name.empty())
    {
        entityList.push_back(npc.at(i));
    }
}

Now I would like the entityList to be sorted in ascending order by the worldY property.
i.e. if npc1 has worldY = 10 and npc2 has worldY = 5, then in the entityList I want to have npc2 and then npc1.
Using the following includes:

#include <algorithm>
#include <iostream>
#include <list>
#include <iterator>

I was thinking of using this:

std::sort(entityList.begin(), entityList.end(), [](Entity e1, Entity e2) 
    {
    // Custom comparison logic 
    return e1.worldY < e2.worldY; // this sorts in ascending order 
    });

But I can’t compile it, because it gives me this error:

Severity Code Description Project File Line Suppression State Details Error C2676 binary '-': 'const std::_List_unchecked_iterator<std::_List_val<std::_List_simple_types<_Ty>>>' does not define this operator or a conversion to a type acceptable to the predefined operator with [ _Ty=Entity ] My2DGame_21 C:Program FilesMicrosoft Visual Studio2022CommunityVCToolsMSVC14.40.33807includealgorithm 8165

I also tried to do this, but the result doesn’t change, I always get the same error:

std::sort(entityList.begin(), entityList.end(), [](const auto& a, const auto& b) { return a.worldY < b.worldY; });

How should I fix my code? I do not know how to do. Is there another way to do this sorting of the list ?