Project Euler

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# [[Problem 7]]

```scheme

#!r6rs

#!chezscheme

(import (chezscheme))

(define (prime? num)

  (if (even? num)

    #f

    (let ((count (isqrt num)))

      (let loop ((check-num 3))

        (cond

          [(< count check-num) #t]

          [(zero? (mod num check-num)) #f]

          [else (loop (+ check-num 2))])))))

(define answer-7

  (let loop ((current 3) (count 1) (prime 2))

    (if

      (= 10001 count)

      prime

      (let ((next (+ current 2)))

        (if (prime? current)

          (loop next (add1 count) current)

          (loop next count prime))))))

(printf "7: ~D~%" answer-7)

```