anchor.diff:          (cons (car lst) store)))
       (reverse store)))
   
  -
  -
  -
   ;;
   ;; Question
   ;;
  
positive.code:         (cons (car xs) store)))
      (reverse store)))
  
  
  
  ;;
  ;; Question
  
negative.code: ;;
  ;; Question
  ;;
  ;;  Define a procedure that takes two lists as input and returns the list of
  ;;  their pairwise averages. Use only MAPCAR, LAMBDA and arithmetic operations
  ;;  in your definition.
  ;;
  
  (defun p-avg (lstA lstB)
    "computes the pairwise average of lstA and lstB"
    (mapcar
      #'(lambda (x y) (float (/ (+ x y) 2)))
      lstA
      lstB))
  
  ;;
  ;; Question
  ;;
  ;; Define LENGTH using MAPCAR, LAMBDA, + and APPLY.
  ;;
  
  (defun mlength (lst)
    (apply
      #'+
      (mapcar
        #'(lambda (x) 1)
        lst)))
  
  ;; This gets "The variable X is defined but never used." warning. If you don't like this, you can define your lambda as: 
  
  ;; (lambda (x) (declare (ignore x)) 1) 
  ;; or
  ;; (lambda (x) (and x 1))
  ;;
  ;; In any case, this warning is totally harmless.
  ;;
  
  
  ;;
  ;; Question
  ;;
  ;; Define your own REMOVE-IF.
  ;;
  
  