02-28.rkt

;; CIS352 -- 2/28/23
#lang racket

(define x
  (hash "A" (set "B" "C")
        "B" (set "C" "A")
        "C" (set "B")))

(define (count-edges graph)
  (foldl
   (λ (key acc)
     (+ acc (length (set->list (hash-ref graph key)))))
   0
   (hash-keys graph)))

(define (count-symmetric-edges graph)

  (foldl
   ;; x is each node (root), acc is the total # of
   ;; symmetric edges
   (λ (x acc)
     (foldl
      ;; y is a node within the set of values pointed to
      ;; by x in the graph, add 1 to acc if (x,y) is a
      ;; symmetric link, add 0 to acc otherwise
      (λ (y acc)
        ;; have edges (x,y)
        ;; generalize to transitive closure
        ;; find all edges (y,z)
        ;; fold over the zs and add (x,z) to graph
        ;; (add another foldl)
        (if (set-member? (hash-ref graph y) x)
            (+ 1 acc)
            acc))
      acc
      (set->list (hash-ref graph x))))
   0
   (hash-keys graph)))
     
(define (h g)
  (if (equal? (one-step-transitive-add g) g)
      g
      (h (one-step-transitive-add g))))


  #;(define (for-each-key keys)
    (match keys
      ['() 0]
      [`(,fst ,rest-keys ...)
       (define number-of-nodes-to-which-key-points
         (length (set->list (hash-ref graph fst))))
       (+ number-of-nodes-to-which-key-points
          (for-each-key rest-keys))]))
    #;(for-each-key (hash-keys graph))