(module gotos-cc mzscheme
  
  ;; Trying to encode the spirit of
  ;;
  ;; 10 PRINT "HELLO WORLD"
  ;; 20 GOTO 10
  ;;
  ;; using Scheme's continuations.

  (define (program-1 end)
    (let ([line-10 #f] [line-20 #f] [line-end #f])
      (let/cc def-k
        (begin 
          (let/cc k (set! line-10 k) (def-k))
          (printf "hello world\n")
          (line-20)))
      (let/cc def-k
        (begin
          (let/cc k (set! line-20 k) (def-k))
          (line-10)))
      (let/cc def-k
        (begin
          (let/cc k (set! line-end k) (def-k))
          (end)))
      line-10))
  
  
  ;; Trying to encode the spirit of
  ;;
  ;; 10 GOTO 20
  ;; 20 PRINT "HELLO WORLD"
  ;;
  ;; using Scheme's continuations.
  (define (program-2 k-end)
    (let ([line-10 #f]
          [line-20 #f]
          [line-end #f])
      (let/cc def-k
        (begin
          (let/cc k (set! line-10 k) (def-k))
          (line-20)))
      (let/cc def-k
        (begin
          (let/cc k (set! line-20 k) (def-k))
          (printf "hello world\n")
          (line-end)))
      (let/cc def-k
        (begin
          (let/cc k (set! line-end k) (def-k))
          (k-end)))
      line-10))
  
  (define (run prog)
    (let/ec end ((prog end)))))