Re: Returning a Pointer to a Struct

From:
pjb@anevia.com (Pascal J. Bourguignon)
Newsgroups:
comp.lang.c++
Date:
Mon, 21 Sep 2009 10:58:36 +0200
Message-ID:
<7c1vm0smgz.fsf@pbourguignon.lefevre.anevia.com>
Spiffy <sylvesterc@gmail.com> writes:

When I created a function to return a pointer to a Struct, GCC returns
"error: cannot convert =E2=80=98linklist::node*=E2=80=99 to =E2=80=98node=

 linklist::*=E2=80=99 in

return" about the return line. I have tried a bunch of things to no
avail. This is a three part question.
   1) What it would take to get the code below to compile?
   2) How come within this function, I needed to specify class name
when referring to the Struct, while other public or private function
doesn't have to?
   3) Ideally, I would keep the Struct private, but that caused more
compiler error. Is this possible?

Thanks!

   class linklist {
   public:
    struct node {
        int data;
        node *link;
    };
    linklist();
    ~linklist();
    void append( int num );
   private:
    struct node *p;
    struct node *addnode( int num );
  };

   struct node linklist::*addnode ( int num ) {


This is parsed as:

    ((struct node) linklist::*) addnode ( int num )

The of the result is ((struct node) linklist::*) which means a
pointer to a member of the class linklist, which points to a struct
node.

To return such a type, you would have to declare a member to the class
linklist:

    */
    class linklist{
    private:
       struct node myNode;
    /*

and return it:

    */
    struct node linklist::*addnode ( int num ) {
         return(*myNode);
    }
    /*

which of course is not what you want, so one wonders why you write
such as return type...

     linklist::node *t;
    return (linklist::node*)t;

You don't need to qualify the names in the same class as the method in
its body. Of course, this would be true only if it was a method of
that class, and not a normal function. For this, you would have to write:

    struct node* linklist::addnode ( int num ) {
        node* t=new node();
        return(t);
    }

--
__Pascal Bourguignon__

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