;; Very ugly port of https://github.com/guicho271828/life10-benchmarks/blob/master/life.ros

(import (rnrs bytevectors))

;;; life.scm -- Conway's Game of Life in Scheme (at least R5RS and later)
;; this let was not needed
(let ((n 40)
      (m 80)
      (g 66000))

(define-syntax dotimes
  (syntax-rules ()
    ((_ (start goal) body ...)
     (let loop ((start 0))
       (when (< start goal)
     body ...
     (loop (+ start 1)))))))

(define-syntax aref*
  (syntax-rules ()
    ((_ a i j)
     (bytevector-u8-ref a (+ (* i m) j)))))

(define-syntax aset!
  (syntax-rules ()
    ((_ a i j v)
     (bytevector-u8-set! a (+ (* i m) j) v))))

(define (display-it b)
  (dotimes (i n)
    (dotimes (j m)
      (if (eq? 0 (aref* b i j))
          (display #\space)
          (display #\*)))
    (newline)))


(define (main)
  (let ((b     (make-bytevector (* n m)))
        (nextb (make-bytevector (* n m))))
    (aset! b 19 41 1)
    (aset! b 20 40 1)
    (aset! b 21 40 1)
    (aset! b 22 40 1)
    (aset! b 22 41 1)
    (aset! b 22 42 1)
    (aset! b 22 43 1)
    (aset! b 19 44 1)
    (display "Before:")
    (display-it b)

    (let loop ((k 0)
           (b b)
           (nextb nextb))
      (when (< k g)
    (dotimes (i n)
      (let* ((nm1 (1- n))
         (up (if (not (eq? i 0))
             (1- i)
             nm1))
         (upm (* up m))
         (down (if (not (eq? i nm1))
               (1+ i)
               0))
         (downm (* down m))
         (im (* i m)))

        (dotimes (j m)
          (let* ((mm1 (1- m))
             (left (if (not (eq? j 0))
                   (1- j)
                   mm1))
             (right (if (not (eq? j mm1))
                (1+ j)
                0))
             (count
              (+ (bytevector-u8-ref b (+ upm  left))
             (bytevector-u8-ref b (+ upm  j))
             (bytevector-u8-ref b (+ upm  right))
             (bytevector-u8-ref b (+ im   right))
             (bytevector-u8-ref b (+ downm right))
             (bytevector-u8-ref b (+ downm j))
             (bytevector-u8-ref b (+ downm left))
             (bytevector-u8-ref b (+ im   left)))))
        (aset! nextb i j
               (cond
             ((eq? count 2) (aref* b i j))
             ((eq? count 3) 1)
             (else 0)))))))
    (loop (1+ k) nextb b)))

    (display "After ") (display g) (display " generations:") (newline)
    (display-it b)))

(main)
)