Question

I am trying to write a function called unzip that takes a list and evaluates to a list of two lists that have alternating elements of the original list.

so far this is what i have:

(define (unzip lst)
    (if (null? lst)
        '()
        (...

this is how it should work:

(unzip ‘(1 a 2 b 3 c)) should evaluate to ((1 2 3) (a b c))

Answer 1

What you have is on the wrong track, sorry. (Think about what the result should be if given an empty input.) Similar to my answer to your last question, here’s a skeleton solution:

(define (unzip l)
  (if (null? l) ???
      (let ([next (unzip ???)])
        (list (cons ??? ???) ???))))

Fill in the ???s appropriately. (Yes, my solution is tested and works for both odd and even inputs.)