Chapter 2, Building Abstractions with Data
Section - 2.2 - Hierarchical Data and the Closure Property
Exercise 2.51
Note that I am using transform-painter from the sicp package of Dr Racket. Its arguments are slightly different from the transform-painter code given in the book.
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(define (below painter1 painter2)
(let ((split-point (make-vect 0.0 0.5)))
(let ((paint-bot
( (transform-painter
(make-vect 0.0 0.0)
(make-vect 1.0 0.0)
split-point
)
painter1
)
)
(paint-up
( (transform-painter
split-point
(make-vect 1.0 0.5)
(make-vect 0.0 1.0)
)
painter2
)
)
)
(lambda (frame)
(paint-bot frame)
(paint-up frame)
)
)
)
)
Alternative implementation of below using ‘beside` and rotations:
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(define (below-alt painter1 painter2)
(rotate90 (beside (rotate270 painter1) (rotate270 painter2)))
)