;; Merge two sorted lists of numbers and delete duplicates

(define merge
  (lambda (lst1 lst2)
    (cond ((null? lst1) (remove-adjacent-duplicates lst2))
          ((null? lst2) (remove-adjacent-duplicates lst1))
          ((< (car lst1) (car lst2))
           (cons-if-different (car lst1) (merge (cdr lst1) lst2)))
          (else
           (cons-if-different (car lst2) (merge  lst1 (cdr lst2)))))))

(define cons-if-different
  (lambda (e lst)
    (if (equal? e (car lst))
        lst
        (cons e lst))))

(define remove-adjacent-duplicates
  (lambda (lst)
    (cond ((null? lst) '())
          ((null? (cdr lst)) lst)
          (else (cons-if-different (car lst) 
                                   (remove-adjacent-duplicates (cdr lst)))))))