(define make-graph
  (make-encapsulation
    (n)
    ((v (generate-vector (lambda (i) (make-vector 3 '())) n)))
    ((node-ref
       (lambda (node i) (vector-ref (vector-ref v node) i)))
     (node-set!
       (lambda (node i value)
         (vector-set! (vector-ref v node) i value))))
    ((number-of-nodes (lambda () n))
     (for-each-node (lambda (function) (for-each-integer function n)))
     (self-print (lambda () (vector-for-each print v)))
     (self (lambda () v))
     (label (lambda (node) (node-ref node 0)))
     (set-label! (lambda (node value) (node-set! node 0 value)))
     (predecessor (lambda (node) (node-ref node 1)))
     (set-predecessor! (lambda (node value) (node-set! node 1 value)))
     (adjacency-list (lambda (node) (node-ref node 2)))
     (first-node (lambda (link) (vector-ref link 0)))
     (second-node (lambda (link) (vector-ref link 1)))
     (link-length (lambda (link) (vector-ref link 2)))
     (reverse-link
       (lambda (link)
         (vector (vector-ref link 1) (vector-ref link 0) (vector-ref link 2))))
     (add-directed-link
       (lambda (link)
         (let ((node1 (first-node link)))
           (vector-set! (vector-ref v node1) 2
                        (cons link (adjacency-list node1))))))
     (add-undirected-link
       (lambda (link)
         (let ((node1 (first-node link))
               (node2 (second-node link)))
           (vector-set! (vector-ref v node1) 2
                        (cons link (adjacency-list node1)))
           (vector-set! (vector-ref v node2) 2
                        (cons (reverse-link link) (adjacency-list node2))))))
     (for-each-link-of-node
       (lambda (function node)
         (for-each function (adjacency-list node)))))))

;@
;;;==========================================
;;;
;;;         Random Graph Generators
;;;
;;;==========================================

(define (random-edge n length)
  (let loop ((i (random n))
             (j (random n)))
    (if (= i j)
        (loop (random n) (random n))
        (vector i j (random length)))))

(define (d-graph n m . r)
  (let* ((r (if (null? r) 100 (car r)))
         (graph (make-graph n))
         (add (graph 'add-directed-link))
         (add-random-link
           (lambda (x) (add (random-edge n r)))))
    (for-each-integer add-random-link m)
    graph))

(define (u-graph n m . r)
  (let* ((r (if (null? r) 100 (car r)))
         (graph (make-graph n))
         (add (graph 'add-undirected-link))
         (add-random-link
           (lambda (x) (add (random-edge n r)))))
    (for-each-integer add-random-link m)
    graph))