;;; Questao 1

(defun dist (peixe)
  (let ((x (first peixe))
	(y (second peixe))
	)
    (sqrt (+ (* x x) (* y y)))
    )
  )

(defun raio (peixes n)
  (first-n n (sort (mapcar #'dist peixes) #'<))
  )

(defun first-n (n lista)
  (if (null lista)
      nil
    (or (nth (1- n) lista)
	(car (last lista))
	)
    )
  )

;;; Questao 2

(defun violacao (lista restricoes)
  (cond
   ((null restricoes) nil)
   ((viola lista (car restricoes)) (car restricoes))
   (t (violacao lista (cdr restricoes)))
   )
  )

(defun viola (lista restricao)
  (not (subset2 restricao lista))
  )

(defun subset2 (restricao lista)
  (member (second restricao)
	  (member (first restricao) lista)
	  )
  )

;;; Questao 3

(defun net-value (mov conta t1 t2)
  "net value for an account in a transaction"
  (let ((md (first mov))
	(mp (second mov))
	(mt (third mov))
	(mv (fourth mov))
	)
    (cond
     ((and (eql conta md) (eql conta mp) 0))
     ((< mt t1) 0)
     ((> mt t2) 0)
     ((eql conta md) (- v))
     ((eql conta mp) v)
     (t 0)
     )
    )
  )

(defun saldo (lista conta t1 t2)
  (apply #'+ (mapcar #'(lambda (x) (net x conta t1 t2)) lista))
  )

;;; Questao 4

(defun soma-impares (x)
  (if (>= x 1)
      (soma-aux 1 x)
    0
    )
  )

(defun soma-aux (i x)
  (if (> i x)
      0
    (+ i (soma-aux (+ i 2) x))
    )
  )