> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/sidef-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/sidef-lang/programming_tasks/2/24_game.md).

# 24 game

```ruby
const digits  = (1..9 -> pick(4))
const grammar = Regex(
    '^ (?&exp) \z
      (?(DEFINE)
          (?<exp> ( (?&term) (?&op) (?&term) )+ )
          (?<term> \( (?&exp) \) | [' + digits.join + '])
          (?<op> [\-+*/] )
      )', 'x'
)
 
say "Here are your digits: #{digits.join(' ')}"
 
loop {
    var input = read("Expression: ", String)
 
    var expr = input
    expr -= /\s+/g     # remove all whitespace
 
    if (input == 'q') {
        say "Goodbye.  Sorry you couldn't win."
        break
    }
 
    var given_digits = digits.map{.to_s}.sort.join
    var entry_digits = input.scan(/\d/).sort.join
 
    if ((given_digits != entry_digits) || (expr !~ grammar)) {
        say "That's not valid"
        next
    }
 
    given(var n = eval(input)) {
        when (24) { say "You win!"; break }
        default   { say "Sorry, your expression is #{n}, not 24" }
    }
}
```

#### Output:

```
Here are your digits: 8 2 3 4
Expression: 8 * (2 - (3 + 4))
Sorry, your expression is -40, not 24
Expression: 8 * (2 - (3 -
That's not valid
Expression: 8 * (2 - (3 - 4))
You win!
```