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// DATUM //
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listlink
    var/value
    var/link

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// COMMANDS //
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//  Creates a new list link with value V.
proc/LinkedList(V)
    var/listlink/l  = new()
    l.value         = V
    return l


//  Adds a value to list link L. If L already has a value,
//  a new link is made and attached to L, which contains V.
proc/LinkedList_Add(listlink/L, V)
    if (!L.value)
        L.value = V

    else if (!L.link)
        L.link = LinkedList(V)

    else if (L.link)
        LinkedList_Add(L.link, V)


//  Searches the list starting at link L for value V.
//  If V is found in a link, the link previously checked
//  will then contain the link of the current linknode.
//  M is optional, but required if starting at the middle
//  of the list.
proc/LinkedList_Remove(listlink/L, V, listlink/M)
    if (L)
        if (L.value == V)
            if (M)
                M.link = L.link
            else
                return L.link

        else if (L.link)
            return LinkedList_Remove(L.link, V, L)

        return L


//  Debugs the list by printing out the values to the world.
//  V stands for the index of the list not used by user).
proc/LinkedList_Print(listlink/L, V=1)
    if (V==1)
        world << "Printing list:"
    if (L)
        if (L.value)
            world << "[V]: [L.value]"
        if (L.link)
            LinkedList_Print(L.link, V+1)
    else
        world << "List does not exist (anymore)."


////////////////////////////////////////////
// DEBUG (REMOVE IF USING THE CODE ABOVE) //
////////////////////////////////////////////

client/New()
    ..()
    var/d   = LinkedList()          //  Create a new list link
    LinkedList_Add(d,10)          //  Add 10 to current link
    LinkedList_Add(d,20)          //  Add 20 to link (makes new one)
    LinkedList_Add(d,30)          //  Add 30 to link (makes new link from new link)

    d = LinkedList_Remove(d,10)       //  Remove 10 from the list (returns L.link)
    d = LinkedList_Remove(d,20)       //  Remove 20 from the list (returns L.link.link)
    d = LinkedList_Remove(d,40)       //  40 not found.

    LinkedList_Print(d)             //  Prints 30.