sicp-solutions/ex-2.51.scm

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1.4 KiB
Scheme

#lang sicp
(#%require sicp-pict)
(define (xcor-vect v) (vector-xcor v))
(define (ycor-vect v) (vector-ycor v))
(define (add-vect u v)
(make-vect (+ (xcor-vect u) (xcor-vect v))
(+ (ycor-vect u) (ycor-vect v))))
(define (sub-vect u v)
(make-vect (- (xcor-vect u) (xcor-vect v))
(- (ycor-vect u) (ycor-vect v))))
(define (scale-vect s v)
(make-vect (* s (xcor-vect v))
(* s (ycor-vect v))))
(define (transform-painter painter origin corner1 corner2)
(lambda (frame)
(let ((m (frame-coord-map frame)))
(let ((new-origin (m origin)))
(painter (make-frame
new-origin
(sub-vect (m corner1) new-origin)
(sub-vect (m corner2) new-origin)))))))
; remember 1 is BELOW 2
(define (below-a painter1 painter2)
(lambda (frame)
(let ((paint-lo (transform-painter painter1
(make-vect 0.0 0.0)
(make-vect 1.0 0.0)
(make-vect 0.0 0.5)))
(paint-hi (transform-painter painter2
(make-vect 0.0 0.5)
(make-vect 1.0 0.5)
(make-vect 0.0 1.0))))
(paint-lo frame)
(paint-hi frame))))
(define (below-b painter1 painter2)
(rotate270 (beside (rotate90 painter2) (rotate90 painter1))))