avoid parameters

2017/d10/main.rkt

@@ -9,37 +9,37 @@
                           datum)
                      #,@(cdr lines))))
 
+(define vec #f)
+(define (set-knot-range! int) (set! vec (list->vector (range int))))
+
 (define-macro (#%mb STARS RANGE STR)
   #`(#%module-begin
      (set-knot-range! RANGE)
      ((if (eq? 'STARS '★) one-star two-star) STR)))
 
 (define (one-star str)
-  (for ([len (in-port read (open-input-string (string-replace str "," " ")))])
-    (reverse-segment len))
+  (define lens (for/list ([len (in-port read (open-input-string (string-replace str "," " ")))])
+                 len))
+  (reverse-segments lens)
   (* (vector-ref vec 0) (vector-ref vec 1)))
 
 (define (two-star str)
   (define ascii-chars (map char->integer (string->list str)))
-  (for* ([round (in-range 64)]
-         [len (in-list (append ascii-chars '(17 31 73 47 23)))])
-    (reverse-segment len))
+  (reverse-segments (append ascii-chars '(17 31 73 47 23)) #:count 64)
   (define dense-hash (for/list ([i (in-range 16)])
                        (apply bitwise-xor (for/list ([v (in-vector vec (* i 16) (* (add1 i) 16))])
                                             v))))
   (string-append* (for/list ([num (in-list dense-hash)])
                     (~r num #:base 16 #:min-width 2 #:pad-string "0"))))
 
-(define vec #f)
-(define current-position (make-parameter 0))
-(define skip-size (make-parameter 0))
-(define (set-knot-range! int) (set! vec (list->vector (range int))))
-
-(define (reverse-segment len)
+(define (reverse-segments lens #:count [count 1])
+  (for*/fold ([current-position 0]
+              [skip-size 0])
+             ([i (in-range count)]
+              [len (in-list lens)])
     (define posns (for/list ([i (in-range len)])
-                  (modulo (+ (current-position) i) (vector-length vec))))
+                    (modulo (+ current-position i) (vector-length vec))))
     (for ([val (in-list (map (curry vector-ref vec) posns))]
           [posn (in-list (reverse posns))])
       (vector-set! vec posn val))
-  (current-position (+ (current-position) len (skip-size)))
-  (skip-size (add1 (skip-size))))
+    (values (+ current-position len skip-size) (add1 skip-size))))