Transpose a matrix in racket (list of lists

Question

I got a list of lists in racket and have to transpose them.

(: transpose ((list-of(list-of %a)) -> (list-of (list-of %a))))

(check-expect (transpose (lis         


        

Answer 1

(define (tr ls)
  (if (empty? (car ls)) empty
 (if (null? ls) empty
     (cons (map car ls) (tr (map cdr ls))))))