Project Euler

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# [[Problem 10]]

```scheme

#!r6rs

#!chezscheme

(import (chezscheme))

(define (sum-prime prime?-table)

  (let* ((len (vector-length prime?-table))

         (index-list (iota len))

         (prime?-list (vector->list prime?-table)))

    (fold-left

      (lambda (sum index prime?)

        (if prime?

          (+ sum index)

          sum))

      0

      index-list

      prime?-list)))

(define answer-10

  (let ((table (make-vector 2000001 #t))

        (count (isqrt 2000000)))

    (vector-set! table 0 #f)

    (vector-set! table 1 #f)

    (let loop1 ((index 2))

      (cond

        [(< count index) (sum-prime table)]

        [(vector-ref table index)

         (let loop2 ((current (* index 2)))

           (cond

             [(< 2000000 current)

              (loop1 (add1 index))]

             [else

               (vector-set! table current #f)

               (loop2 (+ current index))]))]

        [else (loop1 (add1 index))]))))

(printf "10: ~D~%" answer-10)

```