codepad

Language:

; one-time pad

(define-syntax for
  (syntax-rules ()
    ((for (var first past step) body ...)
      (let ((ge? (if (< first past) >= <=)))
        (do ((var first (+ var step)))
            ((ge? var past))
          body ...)))
    ((for (var first past) body ...)
      (let* ((f first) (p past) (s (if (< first past) 1 -1)))
        (for (var f p s) body ...)))
    ((for (var past) body ...)
      (let* ((p past)) (for (var 0 p) body ...)))))
(define (undigits ds . args)
  (let ((b (if (null? args) 10 (car args))))
    (let loop ((ds ds) (n 0))
      (if (null? ds) n
          (loop (cdr ds) (+ (* n b) (car ds)))))))

(define *n*
  (let ((p 18446744073709551359)
        (q 18446744073709551427))
    (* p q)))

(define *s* 20131217) ; rip mom

(define (bbs)
  (set! *s* (modulo (* *s* *s*) *n*))
  (modulo *s* 2))

(define (rand-letter)
  (let loop ((i 26) (ds (list)))
    (if (positive? i)
        (loop (- i 1) (cons (bbs) ds))
        (let ((m (undigits ds 2)))
          (if (< 67108860 m)
              (rand-letter)
              (integer->char
                (+ (modulo m 26) 65)))))))

(define (one-time-pad rows cols)
  (for (r 0 rows)
    (for (c 0 cols)
      (for (j 0 5)
        (display (rand-letter)))
      (display #\space))
    (newline)))

(one-time-pad 40 6)

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