As an exercise in http://ddili.org/ders/d.en/pointers.html, I was implementing a very stripped down version of singly linked list like below:
struct Node(T)
{
    T item;
    Node!T* next_item;
}

string to_string(T)(in Node!T node)
{
    import std.format;
    return node.nextItem ? "%s -> %s".format(node.item, *(node.nextItem))
                         : "%s".format(node.item);

}

struct Forward_List(T, N = size_t)
{
    Node!T* head;
    N size;
}

string to_string(T, N = size_t)(ref Forward_List!(T, N) list)
{
    //todo
    import std.format;
    return "head*: %s, size: %s)".format(&list, list.size);
}

void push_front(T, N = size_t)(ref Forward_List!(T, N) list, T item)
{
    list.head = new Node!T(item, list.head);
    ++list.size;
}

1. If you have noticed, I am needlessly repeating `N = size_t` in to_string and push_front. If I leave the signature like these, is it actually going to affect the structure in anyway?:
void push_front(T, N = size_t)(ref Forward_List!(T, N) list, T item);
string to_string(T, N = size_t)(ref Forward_List!(T, N) list);

2. How does one make it "allocator aware"? What other allocators can I use?

On Saturday, 30 December 2017 at 15:00:32 UTC, helxi wrote:
> As an exercise in http://ddili.org/ders/d.en/pointers.html, I was implementing a very stripped down version of singly linked list like below:
> struct Node(T)
> {
>     T item;
>     Node!T* next_item;
> }
>
> [...]

Correction, I meant:
If I leave the signature like
> these, is it actually going to affect the structure in anyway?:
> void push_front(T, N)(ref Forward_List!(T, N) list, T item);
> string to_string(T, N)(ref Forward_List!(T, N) list);