is_num = (s):
  x = s ord(0)
  if (x >= "0"ord && x <= "9"ord): true.
  else: false.
  .

nums = (s):
  res = ()
  0 to (s length, (b):
    c = s(b)
    if (is_num(c)):
      res push(c).
  .)
  res.

try = 1
while (true):
  r = rand string
  digits = (r(0),r(1),r(2),r(3))
  "\nMy next four digits: " print
  digits join(" ") say
  digit_s = digits ins_sort string

  ("Your expression to create 24 (try ", try, "): ") print
  entry = read slice(0,-1)
  expr = entry eval
  parse = nums(entry)
  parse_s = parse clone ins_sort string
  try++
  if (parse length != 4):
    ("Wrong number of digits:", parse) say.
  elsif (parse_s != digit_s):
    ("Wrong digits:", parse) say.
  elsif (expr == 24):
    "You won!" say
    entry print, " => 24" say
    return().
  else:
    (entry, " => ", expr string, " != 24") join("") say.
.