(define random-list
  0 -> []
  M -> [(1+ (RANDOM 20)) | (random-list (1- M))])

(define random-array
  0 _ -> []
  N M -> [(random-list M) | (random-array (1- N) M)])

(define array->list
  _    []                 -> []                                  \ "end outer loop" \
  Stop [[]          | Ra] -> (array->list Stop Ra)               \ "outer loop" \
  Stop [[Stop | _ ] | _ ] -> []                                  \ "break out from inner loop" \
  Stop [[X    | Rl] | Ra] -> [X | (array->list Stop [Rl | Ra])]) \ "inner loop" \

(array->list 20 (random-array 10 10))