Scheme/DrRacket

How do you do this shit /prog/?

Write a Scheme function evens-odds (using at least one abstract list function), which consumes a list of numbers lst and produces the difference between the sum of the odd numbers and the sum of the even numbers in the list lst. Some examples follow:


(evens-odds (list 1 2 3 4)) => -2
(evens-odds empty) => 0
(evens-odds (list 2 4 16)) => -22
(evens-odds (list 1 3 7 21 13)) => 45


Note: You should use local function(s) only (in case of need).

Be cool, and write something like this instead of filtering/reducing twice:

(define (evens-odds l)
  (define (f x a) ((if (odd? x) + -) a x))
  (foldl f 0 l))

I'm not going to explain my code because that would be HELPING HIM.