How to get a reference in a struct of the same struct in my code

Question

I have this struct, but I get some errors when I mention a reference to its own type:

struct Point  {
              int x;
              int y;

              bool isLattice;

              Vect2D gradient;

              ///used only when isLattice is false
              Point p00; ///top-left corner
              Point p01; ///top-right corner
              Point p10; ///bottom-left corner
              Point p11; ///bottom-right corner

              ///the displacement vectors  Gradient-this.Vect2D
              Vect2D disp00;
              Vect2D disp01;
              Vect2D disp10;
              Vect2D disp11;  ///used along the gradient vector of the lattice points

              ///the Q-s for each corner Q= Disp*G which are going to be used for the interpolation
              double q00;
              double q01;
              double g10;
              double q11;

          };

I need to know how I should initialize this struct, because this is how I used to do it in the past in other codes. What is the error in this one?

I suppose telling us what the errors are, and how you are initialising it would be too much to ask? — , Jan 27 '17 at 21:29
When I try to initialize Point p00 for example , it says it has incomplete type — Andrew Stef, Jan 27 '17 at 21:31
You must have done that in a different language. Such a structure would be infinitely large in C++. — molbdnilo, Jan 27 '17 at 21:32

score 2 · Answer 1 · answered Jan 27 '17 at 21:35

2

I would guess you're coming from a managed language

struct Point  {
    //...
    Point p00; 
    // ...
}

This is your problem. Objects in C++ are NOT references. This puts an instance of Point inside an instance of Point. How will that work? You could use a pointer, or a reference.

Change

Point p00;

to

Point & p00; // this requires being initialized  
             // in the constructor initialization list

or maybe

std::shared_ptr<Point> p00;

answered Jan 27 '17 at 21:35

Rob K

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If you haven't already, get [a good C++ book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list?lq=1) and forget everything you know about whatever language you already know. – Rob K Jan 27 '17 at 21:38
I'd pitch a `std::unique_ptr` over the `std::shared_ptr`. Doesn't seem to be any need to share ownership. – user4581301 Jan 27 '17 at 22:00
@user4581301 It appeared to me that the pointers were coming from somewhere else, so ownership was unclear. – Rob K Jan 29 '17 at 18:03

score 0 · Answer 2 · answered Jan 27 '17 at 21:38

0

Change Point pX; to Point * pX;.

This way, the code will compile, and you get to initialise the Point pointers using an appropriate constructor.

answered Jan 27 '17 at 21:38

Tasos Papastylianou

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score -1 · Answer 3 · answered Jan 27 '17 at 21:40

-1

Why dont you use another type struct in instances of Point?

answered Jan 27 '17 at 21:40

Jose María López Bonaque

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How to get a reference in a struct of the same struct in my code

3 Answers3