1. função intercala

(defun intercala (lista1 lista2)
  (if (null lista1)
      ()
      (cons (car lista1)
            (cons (car lista2)
                  (intercala (cdr lista1) (cdr lista2))
            )
      )
  )
)


2. desenhar repr. gráfica

(((A . B). C).(A . (C . B)))

 _______          _______
|   |   |	 |   |   |
| . | .------>	 | A | . |
| | |   |	 |   | | |
 -|-----	  -----|-
  |		       | 
  V                    V
 _______          _______
|   |   |	 |   |   |
| . | C |	 | C | B |
| | |   |	 |   |   |
 -|-----	  -------
  |		         
  V
 _______
|   |   |
| A | B |
|   |   |
 -------


((A) B (C D) ((E) F))


 _______      _______      _______      _______ 
|   |   |    |   |   |	  |   |   |    |   |  /|
| . | .----> | B | .----> | . | .----> | . | / |
| | |   |    |   |   |	  | | |   |    | | |/  |
 -|-----      ------- 	   -|-----      -|----- 
  |                         |            |
  V                         V            V
 _______                   _______      _______      _______ 
|   |  /|		  |   |   |    |   |   |    |   |  /|
| A | / |		  | C | . |    | . | .----> | F | / |
|   |/  |		  |   | | |    | | |   |    |   |/  |
 -------		   -----|-      -|-----      ------- 
                                |        |
                                V        V
                           _______      _______ 
			  |   |  /|    |   |  /|
			  | D | / |    | E | / |
			  |   |/  |    |   |/  |
			   -------      ------- 

3. função ncaixas

(defun ncaixas (s-expr)
  (if (atom s-expr)
      0
      (+ 1
         (ncaixas (car s-expr))
         (ncaixas (cdr s-expr))
      )
  )
)


4. produto de polinômios

(defun prod (poli1 poli2)
  (if (null prod1)
      ()
      (soma (mult-escalar (car poli1) poli2)
            (cons 0 (prod (cdr poli1) poli2)
      )
  )
)

(defun soma (poli1 poli2)
  (cond
    ((null poli1)  poli2)
    ((null poli2)  poli1)
    (t  (cons (+ (car poli1) (car poli2))
              (soma (cdr poli1) (cdr poli2))
        )
    )
  )
)

(defun mult-escalar (coef poli)
  (if (null poli)
      ()
      (cons (* coef (car poli))
            (mult-escalar coef (cdr poli))
      )
  )
)