Scheme Programming Assignment Write purely functional Scheme functions to: 1) re

Question

Scheme Programming Assignment

Write purely functional Scheme functions to:

   1) return all rotations of a given list. For example, (rotate '(a b c d e)) should return ((a b c d e) (b c d e a) (c d e a b) (d e a b c) (e a b c d)) in some order - not necessarily in the one given in the example.

   2) return a list of all elements of a given list that satisfy a given boolean function. For example (filter (lambda (X) ( < X 5)) '(3 9 5 8 2 4 7)) should return (3 2 4).

Comment your code - in Scheme a comment is anything that follows the ";" (semicolon) character on a line. You comments should include your name and the date in addition to any additinal comments.

Explanation / Answer

1) Scheme code :

(define (rotate lst n)
(cond
[(< n 0)
(error "n is negative")]
[(or (= n 0) (null? lst))
lst]
[else
(rotate (append (cdr lst) (list (car lst)))
(- n 1))]))

Implementation :

(rotate '(a b c d e) 3)
=> '(d e a b c)

(rotate '(a b c) 5)
=> '(c a b)

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