1. Write a function to find the K'th element of a list.
Make K optional and default to the first element.
Example:
* (find-kth '(a b c d) 3)
D


2. Write a function to determine whether its argument is a
prime number.
Example:
* (is-prime 7)
T


3. What does the delete function do?  What is the difference between
delete and remove?



4. Write a function that inserts an element at a given position into a list.
    Example:
    * (insert-at 'alfa '(a b c d) 2)
    (A ALFA B C D)


5. What is the result of (rplacd (car '((a b) c)) 'd)



6. Write a program that defines a 1-dimensional array of length 100
where the values within the array equal the index of each array cell.



7. What does incf do?



8. Define a function with one keyword argument.



9. Describe Lisp packages -- functionality and purpose.  What does
export do?  What does use-package do?



10. Write a macro of one argument that adds 1 to its argument.



11. Write three versions of a program that uses iteration
constructs to create a list containing the numbers 1 through 20.
The three versions should use dotimes, do, and loop.



12. What are the differences between symbols and strings?




13. What are the differences between CLOS objects and defstructs?