[cl-graph-devel] how to subclass vertices, too?

[Gary King]

> Would you believe that:
>
> (1) I needed to make "my-happy-vertex" subclass
> "graph-container-vertex" in order for things to work?

Yes, and I should have mentioned it. Someday I hope to use dynamic  
class creation to ensure that vertexes and so forth extend the  
correct base class but that's up to the user now. (I just updated the  
documentation).

> (2) When so subclassing the vertex class, I have to set the "element"
> slot to be something unique?  Failure to do so seemed to confuse the
> duplicate-prevention machinery.  In fact, I didn't set it at all so it
> was nil (obviously I didn't see this coming), and then things got
> weird as only one of my nil "elemented" vertices was added...

I'm not so sure about this. Maybe this code will make things clearer  
(or not!)

> (in-package cl-graph)
>
> (defclass* my-happy-vertex (graph-container-vertex)
>   ())
>
> (let ((g (make-container 'graph-container :vertex-class 'my-happy- 
> vertex)))
>   (loop for (a b) in '((a b) (c d) (a c) (d e) (f g) (f h) (g i)) do
>         (add-edge-between-vertexes g a b))
>
>   (print "Vertexes")
>     ;; could also use the more generic iterate-nodes
>   (iterate-vertexes g (lambda (x) (print x)))
>
>   (print "Elements")
>   (iterate-elements g (lambda (x) (print x)))
>
>   g)

For me, this prints:

> "Vertexes"
> #<A>
> #<I>
> #<G>
> #<B>
> #<E>
> #<H>
> #<C>
> #<D>
> #<F>
> "Elements"
> A
> I
> G
> B
> E
> H
> C
> D
> F
> #<GRAPH-CONTAINER 9 #xF4AF10E>

The point is that when I call add-edge-between-vertexes <graph>  
<value> <value>, then the graph code takes care of wrapping the  
values into vertexes such that the element of the vertex is the  
value. Does this correspond to what you're doing?

Thanks,
-- 
Gary Warren King
metabang.com
http://www.metabang.com/