[plt-scheme] rotate90 is clockwise on einstein; CCW on zorro

Dear Henderson-users,

OK, this one threw us for a loop.  I loaded soegaard's version of the
Henderson stuff:

(require (planet "sicp.ss" ("soegaard" "sicp.plt" 2 0)))

Then I tried rotate90 on einstein and mark-of-zorro.

einstein gets rotated clockwise, but mark-of-zorro is rotated
counter-clockwise (see attached).


Here is another (related?) anomoly.  In looking at the code for zorro,
it appears that (0,0) is in the lower-left and (1,) is in the
upper-right:

(define mark-of-zorro
 (let ((v1 (make-vect .1 .9))
       (v2 (make-vect .8 .9))
       (v3 (make-vect .1 .2))
       (v4 (make-vect .9 .3)))
   (segments->painter
    (list (make-segment v1 v2)
          (make-segment v2 v3)
          (make-segment v3 v4)))))


But when we tried the diagonal shader, it seems that (0,0) is in the
UPPER-left.  my-diag performs the same as the provided
diagonal-shading:

(define my-diag
 (procedure->painter (lambda (x y) (* 127 (+ x y)))))

Help?

Fred
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