Question

Create a function that returns a boolean value if all-elements are not odd or even.

Using Dr. Racket and the How to Design a Function (HtDF ) recipe, create a function that will return the following check-expect:

(check-expect (all-elements? even? (list 1 2 3) false)

(check-expect (all-elements? even? (list 2 4 6) true)

(check-expect (all-elements? odd? (list 1 3 5) true)

Can you find an element in the list where the predicate fails (return false)?

Answer 1

Using Dr. Racket we can return a list containing(in order)the items of a givenlist for which a given function returns true, example

>(filter even?(list 1 2 3 4))

-(listof number)

'(2 4)

>(filter odd?(list 1 2 3 4))

-(listof number )

'(1 3)

similarly we can apply for the false condition and the above question answer is below:-

(define (all elements ?predicate Ist)

(cond ((empty? lst)true)

((predicate(first Ist)) (all-elements?predicate(cdr Ist)))

(else false)))

DIFFERENT APPROACH

;; make 'and' as a function

(define(my-and a b) (and a b))

(define(all-elements ?predicate args)

(foldr my-and #t (map predicate args)))

(all-elements? odd '(1 3 5))

;;#t

or as a variadic function:

(define(all-elements?predicate.args)

(foldr my-and(map predicate args)))

then one can type :

(all-elements? odd? 1 3 5 7 9);;#t