; a prime number puzzle
(define (two-digit-primes)
(let ((sieve (make-vector 100 #t)))
(do ((p 2 (+ p 1))) ((<= 100 p) (newline))
(when (vector-ref sieve p)
(when (< 10 p) (display p) (display " "))
(do ((i (* p p) (+ i p))) ((<= 100 i))
(vector-set! sieve i #f))))))
(two-digit-primes)