anchor.diff:                    (if (even? x)
                       nil
                       (succ x)))
  -                (range 1 10))
  +                (range :from 1 :to 10))
      out = (2 4 6 8 10)
      ```"
     (let* [(lengths (let* [(out '())]
  
positive.code:    ```"
    (foldl append '() xss))
  
  (defun range (start end)
    "Build a list from START to END.
  
     ### Example:
     ```cl
     > (range 1 10)
     out = (1 2 3 4 5 6 7 8 9 10)
     ```"
    (let* [(out '())]
      (for i start end 1
        (push-cdr! out i))
      out))
  
  (defun reverse (xs)
    "Reverse the list XS, using the accumulator ACC.
  
     ### Example:
     ```cl
     > (reverse (range 1 10))
     out = (10 9 8 7 6 5 4 3 2 1)
     ```"
    (let* [(out '())]
  
negative.code: 
     ### Example:
     ```cl
     > (last (range :from 1 :to 100))
     out = 100
     ```"
    (assert-type! xs list)
  