# Debit Reading Session - SICP solutions pt.1

Posted on June 8, 2021
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59;; 1.41
(define (double f)
(lambda (x)
(f (f x))))

:;; 1.42
(define (compose f g)
(lambda (x)
(f (g x))))

;;; 1.43
(define (repeated f n)
(if (= 1 n)
identity
(comp (repeated f (dec n)))))

;;; 2.27
(define (map-tree node-fn leaf-fn tree)
(cond
((null? tree) tree)
((not (pair? tree)) (leaf-fn tree))
(else
(node-fn
(cons (map-tree node-fn leaf-fn (car tree))
(map-tree node-fn leaf-fn (cdr tree)))))))

(define (map-nodes f tree)
(map-tree f identity tree))

(define (deep-reverse x)
(map-nodes reverse x))

;;; 2.28
(define (flatten tree)
(define (rec acc t)
(cond
((null? t) acc)
((not (pair? t)) (cons t acc))
(else
(rec (rec (cdr t) acc)
(car t)))))
(rec nil tree))

;;; 2.30
(define (square-tree tree)
(map-leaves square tree))

;;; 2.31
(define square-tree map-leaves) ; ha!

;;; 2.32
TODO
``````

FYI: I just typed those in, I didn’t yet test them yet.