7. In the space below, complete the definition of add-between, which takes a lis

Question

7. In the space below, complete the definition of add-between, which takes a list ls and an expression x, and inserts x between every two elements of ls.

Consider the following calls below as examples of its usage.

>(add-between 'and ' (1 2 1 2))

(1 and 2 and 1 and 2)

>(add-between 'and '())

()

>(add-between 'and '(1 1))

(1 and 1)

>(add-between 'and '(1))

(1)

8. Consider the function foo below:

(define foo

(lambda (x y)

(cond

((null? x) y)

((memv (car x) y) (foo (cdr x) y))

(else (cons (car x) (foo (cdr x) y))))))

Which of the following is a better name for foo?

A.union

B. set difference

C.binary XOR

D.append

9. Consider the function bar below:

(define bar

(lambda (x f)

(cond

((not (pair? x)) (f x))

(else (cons (bar (car x) f) (bar (cdr x) f))))))

What is a better name for the the function bar?

A. map-tree

B. cons-cell-count

C. occurs?

D. constant #t (that is, a function which always returns true)

Explanation / Answer

8) Append

9)Map-Tree

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