little_schemer_chapter_5.scheme

(define atom?
  (lambda (a)
    (not (or (null? a) (pair? a)))))

(define rember*
  (lambda (a l)
    (cond
      ((null? l) `())
      ((pair? (car l)) (cons (rember* a (car l)) (rember* a (cdr l))))
      ((eq? (car l) a) (rember* a (cdr l)))
      (else (cons (car l) (rember* a (cdr l)))))))
            
(rember* `cup `((coffee) cup ((tea) cup) (and (hick)) cup))

(rember* `sauce `(((tomato sauce)) ((bean) sauce) (and ((flying)) sauce)))

(define insertR*
  (lambda (new old l)
    (cond
      ((null? l) `())
      ((pair? (car l)) (cons (insertR* new old (car l)) (insertR* new old (cdr l))))
      ((eq? (car l) old) (cons old (cons new (insertR* new old (cdr l)))))
      (else (cons (car l) (insertR* new old (cdr l)))))))
      
(insertR* `roast `chuck `((how much (wood)) could ((a (wood) chuck)) (((chuck))) (if (a) ((wood chuck))) could chuck wood))

(define occur*
  (lambda (a l)
    (cond
      ((null? l) 0)
      ((pair? (car l)) (+ (occur* a (car l)) (occur* a (cdr l))))
      ((eq? (car l) a) (+ 1 (occur* a (cdr l))))
      (else (occur* a (cdr l))))))
      
(occur* `banana `((banana)
  (split ((((banana ice)))
    (cream (banana))
    sherbet))
    (banana)
    (bread)
    (banana brandy)))
    
(define subst*
  (lambda (new old l)
    (cond
      ((null? l) `())
      ((pair? (car l)) (cons (subst* new old (car l)) (subst* new old (cdr l))))
      ((eq? (car l) old) (cons new (subst* new old (cdr l))))
      (else (cons (car l) (subst* new old (cdr l)))))))

(subst* `orange `banana `((banana)
  (split ((((banana ice)))
    (cream (banana))
    sherbet))
    (banana)
    (bread)
    (banana brandy)))
    
(define insertL*
  (lambda (new old l)
    (cond
      ((null? l) `())
      ((pair? (car l)) (cons (insertL* new old (car l)) (insertL* new old (cdr l))))
      ((eq? (car l) old) (cons new (cons old (insertL* new old (cdr l)))))
      (else (cons (car l) (insertL* new old (cdr l)))))))
      
(insertL* `pecker `chuck `((how much (wood)) could ((a (wood) chuck)) (((chuck))) (if (a) ((wood chuck))) could chuck wood))

(define member*
  (lambda (a l)
    (cond
      ((null? l) #f)
      ((pair? (car l)) (or (member* a (car l)) (member* a (cdr l))))
      ((or (eq? (car l) a) (member* a (cdr l)))))))
      
(define leftmost
  (lambda (l)
    (cond
      ((atom? l) l)
      (else (leftmost (car l))))))