How can I access std::function in std::list in C++

Question

I am attempting to answer generate a Template function in C++ which takes in an std::list of std::function (I think). I am however not sure how to understand the datatype I am working with.

According to GDB my datatype is:

type = std::__cxx11::list<std::function<void(std::array<positions, 3>&)>, std::allocator<std::function<void(std::array<positions, 3>&)> > > (*)(const std::array<positions, 3> &)

I can not access the element as an array if I call the input movenents I can not access for example the first element as movement[0] I don't understand why that is since the type looks like a list.

I have tried to access it as an array, and I have tried to read std::list containing std::function and access it with:

for (auto f: movements) {
        (*f)();
    }

The function generating the the list looks like this:

auto movements(const pieces_positions &pieces) {
    auto result = std::list<std::function<void(pieces_positions&)>>{};
    for (auto i=0u; i<pieces.size(); ++i)
        switch(pieces[i]) {
            case positions::pos1:
                result.push_back([i](pieces_positions& pieces){ pieces[i] = positions::pos2; });
                break;
            case positions::pos2:
                result.push_back([i](pieces_positions& pieces){ pieces[i] = positions::pos1; });
                result.push_back([i](pieces_positions& pieces){ pieces[i] = positions::pos3; });
                break;
            case positions::pos3:
                result.push_back([i](pieces_positions& pieces){ pieces[i] = positions::pos2; });
                break;
        }
    return result;
}

Answer 1

Two things (that I think are what you're asking about):

1. The symbol movements is a function that you need to call. You do it by the usual movements(pices).

2. The function objects in the list that the function returns are not pointers that can be dereferenced. You use them as normal functions and call them as such, like f(pieces).

Also, in C++ there's no standard "array-list" like container. A list is a list and can't be indexed like an array or a vector.