Compile errors for double linked list code
<p>I have tried to implement doubly linked list in C++. Here is the code,</p>

<pre><code>#include &lt;iostream&gt;
using namespace std;
//double linked list
class Link{
    public:
        long data;
        Link *next;

    public:
        Link(long d) {
            data=d;
        }
        void displaylink() {
            cout&lt;&lt;data&lt;&lt;" "&lt;&lt;"\n";
        }
};

class firstl {
    private:
        Link *first;
        Link *last;

    public:
        firstl() {
            first=NULL;
            last=NULL;
        }
    public:
        bool empthy() {
            return (first==NULL);
        }

    public:
        void insertfirst(long dd) {
            Link *newlink=new Link(dd);
            if (empthy)
                last=newlink;
            newlink-&gt;next=first;
            first=newlink;
        }

    public :
        void insertlast(long dd) {
            Link *newlink=new Link(dd);
            if (empthy)
                 first=newlink;
            else
                last-&gt;next=newlink;
            last=newlink;
        }


    public :
        long deletefirst() {
            long temp=first-&gt;data;
            if (first-&gt;next==NULL) //if only one item
                last=NULL;//null&lt;-last;
            first=first-&gt;next; //first--&gt;old next;
            return temp;
        }
    public:
        void displaylist() {
            Link *current=first;
            while (current!=NULL) {
                current-&gt;displaylink();
                current=current-&gt;next;
            }
        }
};

int main() {
    firstl linked;
    linked.insertfirst(22);
    linked.insertfirst(44);
    linked.insertfirst(66);
    linked.insertlast(11);
    linked.insertlast(33);
    linked.insertlast(55);
    linked.displaylist();
    linked.deletefirst();
    linked.deletefirst();
    linked.displaylist();
    return 0;
}
</code></pre>

<p>But here are the compile errors:</p>

<pre><code>1&gt;------ Build started: Project: linked)list, Configuration: Debug Win32 ------
1&gt;  linked_list.cpp
1&gt;c:\users\david\documents\visual studio 2010\projects\linked)list\linked_list.cpp(40): error C3867: 'firstl::empthy': function call missing argument list; use '&amp;firstl::empthy' to create a pointer to member
1&gt;c:\users\david\documents\visual studio 2010\projects\linked)list\linked_list.cpp(51): error C3867: 'firstl::empthy': function call missing argument list; use '&amp;firstl::empthy' to create a pointer to member
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
</code></pre>

<p>How can this be fixed?</p>
