/prog/ - [SICP] Ex 1.30 / 1.31

Name: Anonymous 2008-02-10 7:46

Here's what I have



; Ex 1.30

(define (sum term a next b)

  (define (iter a result)

    (if (> a b)

        result

        (iter (next a) (+ result (term a)))))

  (iter a 0))

; Ex 1.31

(define (product term a next b)

  (define (iter a result)

    (if (> a b)

        result

        (iter (next a) (* result (term a)))))

  (iter a 1))



(define (fac n)

  (product (lambda (x) x) 1 (lambda (x) (+ x 1)) n))

Am i rite?

Name: Anonymous 2008-02-12 6:37

OP again, exercise 1.42 & 1.43
Here is what I have



; Ex 1.42

; composes an arbitrary number of procedures



(define (compose . l)

  (lambda (x)

    (define (compose-iter l x)

       (if (null? l) x

           (compose-iter (cdr l) ((car l) x))))

     (compose-iter (reverse l) x)))

Works nicely.

As for exercise 1.43..



; Does scheme have such function? there is a make-string but I cannot find equivalent for lists



(define (make-list x n)

  (define (iter l n)

    (if (= n 0) l

        (iter (cons x l) (- n 1))))

  (iter '() n))



(define (repeated f n)

  (apply compose (make-list f n)))

What do you think?

[SICP] Ex 1.30 / 1.31

1 Name: Anonymous 2008-02-10 7:46

30 Name: Anonymous 2008-02-12 6:37

Name: Anonymous 2008-02-10 7:46

Name: Anonymous 2008-02-12 6:37