anchor.diff:  
   ;;;; Brett Commandeur
   ;;;; 1255891
  -;;;; CMPUt 325 Wi17 - NON-PROCEDURAL PROG LANGUAGES Combined LAB LEC Wi17
  -
  -#|--- TODO: Remove this comment
  -
  -Acceptable built-in functions:
  -
  -(atom x)
  -(null x)
  -(eq x y)
  -(equal x y)
  -(numberp x)
  -(append x y)
  -(car x)
  -- (cadr ...)
  -(cdr x)
  -- (cdaar ...)
  -(cons x y)
  -(if x y z)
  -(cond ...)
  -(let ((x y) (u v)) z)
  -(let* ((x y) (u v)) z)
  -(defun ...)
  -(quote x) and its short form 'x
  -(list x1 x2 ...)
  -(print ...)
  -(sort L fun) % this is useful for the last problem
  -(copy-list L) % useful in conjunction with sort
  -- http://clhs.lisp.se/Body/f_cp_lis.htm#copy-list
  -- (sort (copy-list L) sort-predicate)
  -
  -(+ x y)
  -(- x y)
  -(* x y)
  -(/ x y)
  -(< x y)
  -(> x y)
  -(= x y)
  -(<= x y)
  -(>= x y)
  -(and x y)
  -(or x y)
  -(not x)
  -
  -|#
  +;;;; CMPUT 325 Wi17 LEC B1 - NON-PROCEDURAL PROG LANGUAGES Combined LAB LEC Wi17
   
   ;;; ----------
   ;;; Question 1
  
positive.code:     ((= S 0) T) ; true, if sum == 0
      ((> (car L) S) (is-subset-sum S (cdr L))) ; number too big
  
      (t
        (or
          (is-subset-sum
            S
  
negative.code:         (is-subset-sum
            (- S (car L))
            (cdr L))))))
  