2 files changed, 37 insertions, 17 deletions
diff --git a/shared/lists.rkt b/shared/lists.rkt
index b721623..f8d96d0 100644
--- a/shared/lists.rkt
+++ b/shared/lists.rkt
@@ -4,7 +4,8 @@
          fold-right
          fold-left
          flatmap
-         enumerate-interval)
+         enumerate-interval
+         enumerate-windows)
 (define (append list1 list2)
   (if (null? list1)
     list2
@@ -68,3 +69,27 @@
            (enumerate-interval 1 (- i 1))))
     (enumerate-interval 1 n)))
 
+(define (enumerate-windows seq n)
+  (define (setup-n-window)
+    (define (rec i things)
+      (if (> i n)
+        (list '() things)
+        (let ((setup (rec (+ i 1)
+                          (cdr things))))
+          (cons (cons (car things) (car setup))
+                (cdr setup)))))
+    (rec 1 seq))
+  (define (shift-window w item)
+    (append (cdr w) (list item)))
+  (define (iter result window things)
+    (if (null? things)
+      (cons window result)
+      (iter (cons window result)
+            (shift-window window (car things))
+            (cdr things))))
+  (let ((setup (setup-n-window)))
+    (iter '() (car setup) (cadr setup))))
+
+(enumerate-windows
+  (enumerate-interval 1 4)
+  2)
diff --git a/shared/pict.rkt b/shared/pict.rkt
index 7c7a74e..6eb2e19 100644
--- a/shared/pict.rkt
+++ b/shared/pict.rkt
@@ -7,26 +7,25 @@
   sub-vect
   scale-vect
   test-vect
-  make-frame
   origin-frame
   edge1-frame
   edge2-frame
   test-frame
   make-segment
   start-segment
-  end-segment)
+  end-segment
+  paint
+  segments->painter)
 (require sicp-pict)
 (require "lists.rkt")
 
-(define (make-vect x y)
-  (cons x y))
 (define (xcor-vect v)
-  (car v))
+  (vector-xcor v))
 (define (ycor-vect v)
-  (cdr v))
+  (vector-ycor v))
 
 (define (add-vect . v)
-  (make-vect 
+  (make-vect
     (fold-right + 0 (map xcor-vect v))
     (fold-right + 0 (map ycor-vect v))))
 (define (sub-vect . v)
@@ -40,22 +39,18 @@
              (* s (ycor-vect v))))
 (define test-vect (make-vect 1 2))
 
-(define (make-frame origin edge1 edge2)
-  (list origin edge1 edge2))
 (define (origin-frame frame)
-  (car frame))
+  (frame-origin frame))
 (define (edge1-frame frame)
-  (cadr frame))
+  (frame-edge1 frame))
 (define (edge2-frame frame)
-  (caddr frame))
+  (frame-edge2 frame))
 (define test-frame (make-frame
                      (make-vect 1 2)
                      (make-vect 2 4)
                      (make-vect 3 6)))
 
-(define (make-segment start end)
-  (cons start end))
 (define (start-segment s)
-  (car s))
+  (segment-start s))
 (define (end-segment s)
-  (cdr s))
+  (segment-end s))