(define iota
  (lambda (n)
    (enum-from-to 0 (- n 1))))

(define slots
  (lambda (s)
    (list #\{ (intersperse #\| s) #\})))

(define port
  (lambda (n)
    (list "<" n ">")))

(define record
  (lambda (n)
    (slots (map1 slots n))))

(define attr
  (lambda (a)
    (list #\[
	  (intersperse
	   #\,
	   (map1 (lambda (l)
		   (let ((key (car l))
			 (value (cadr l)))
		     (list key #\= #\" value #\")) )
		 a))
	  #\])))

(define node
  (lambda (l)
    (let ((n (car l))
	  (a (cadr l)))
      (list n #\space (attr a) #\; #\newline))))

(define edge
  (lambda (e)
    (let ((l (car e))
	  (r (cadr e))
	  (a (caddr e)))
      (list l " -> " r #\space (attr a) #\; #\newline))))

(define digraph
  (lambda (g)
    (let ((name (car g))
	  (n (cadr g))
	  (e (caddr g)))
      (list 'digraph #\space name #\space #\{ #\newline
	    (map1 node n)
	    (map1 edge e)
	    #\} #\newline))))