5.3.1. Memory as Vectors
Register machines for count-leaves
Implement register machines for the following procedures. Assume that the list-structure memory operations are available as machine primitives.
(define (count-leaves tree)
(cond ((null? tree) 0)
((not (pair? tree)) 1)
(else (+ (count-leaves (car tree))
(count-leaves (cdr tree))))))
a. Recursive count-leaves:
(define (count-leaves tree)
(define (count-iter tree n)
(cond ((null? tree) n)
((not (pair? tree)) (+ n 1))
(else (count-iter (cdr tree)
(count-iter (car tree) n)))))
(count-iter tree 0))
b. Recursive count-leaves with explicit counter:
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