Question

In: Computer Science

Given the following Scheme definition: (define x '(define (fac n) (if (= n 0) 1 (*...

Given the following Scheme definition:

(define x '(define (fac n)
              (if (= n 0) 1
                  (* n (fac (- n 1))))))

(This does not define the factorial function fac, but the variable x.)

Write Scheme expressions in terms of x that would have the effect of extracting the following expressions:

(fac n)
0
(- n 1)
The second occurrence of fac.
The last occurrence of n.

E.g., the expression (car x) would extract define.

Expert Solution

Given below statements are equivalent.

(car (cdr x) is same as (cadr x)
(car (cdr (cdr x))) is same as (caddr x)
(cdr (cdr x)) is same as (cddr x)
(cdr (cdr (cdr x) is same as (cdddr x)

Below are the scheme expressions and their corresponding output :

1)

(cadr x) ==> (fac n)

2)

(caddr (car (cdr (car (cddr x))))) ==> 0

3)

(cadr (caddr (car (cdddr (car (cddr x)))))) ==> (- n 1)

4)

(car (caddr (car (cdddr (car (cddr x)))))) ==> fac (second occurance)

5)

(cadr (cadr (caddr (car (cdddr (car (cddr x))))))) ==> n (last occurance)

Snapshot showing step by step extractions of scheme expressions: (Tick marked are required ones)

venereology answered 7 months ago

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