2 days ago

my attempt to do the exercises in sicp.

## Tuesday, July 1, 2008

### sicp exercise 1.43

; Exercise 1.43. If f is a numerical function and n is a positive integer, then we can form the nth

; repeated application of f, which is defined to be the function whose value at x is f(f(...(f(x))...)).

; For example, if f is the function x -> x + 1, then the nth repeated application of f is the function

; x -> x + n. If f is the operation of squaring a number, then the nth repeated application of f is the

; function that raises its argument to the 2^nth power. Write a procedure that takes as inputs a procedure

; that computes f and a positive integer n and returns the procedure that computes the nth repeated

; application of f. Your procedure should be able to be used as follows:

; ((repeated square 2) 5)

; 625

; Hint: You may find it convenient to use compose from exercise 1.42.

(define (square x) (* x x))

(define (compose f g)

(lambda(x)

(f (g x))))

(define (repeated f n)

(define (iter i res)

(if (>= i n)

res

(iter (+ i 1) (compose f res))))

(iter 1 f))

(display ((repeated square 2) 5)) (newline)

Subscribe to:
Post Comments (Atom)

## No comments:

Post a Comment