0. #lang racket
1. (require racket/generator)
2. (define id (generator (a b)
3.               (yield (cons a b))))
4. (display (id 2 null))
5. (display (id 3 null))

=>

(2)

result arity mismatch;

expected number of values not received

expected: 1

received: 2

values...:

3

'()