;;add all items in list
(defun sumlist (l)
  ( cond
    ( (null l) 0)
    ( t (+ (car l) (sumlist (cdr l))))
    )
  )
;;demo sumlist
(sumlist '(2 4 6))
;12 
(sumlist '(2 4 6 10 12 14 16))
;64

;;multiply all items in list
(defun multlist (l)
  ( cond
    ( (null l) 1)
    ( t (* (car l) (multlist (cdr l))))
    )
  )
;;demo multlist
(multlist '(2 4 6))
;48
(multlist '(2 4 6 10 12 14 16))
;1290240

;;filer argument and stop after first argument and return the tail
(defun rember (x l)
  ( cond
    ( (null l) l)
    ( (eq x (car l))(cdr l))
    ( t ( cons (car l) (rember x (cdr l))))
    )
  )
;;demo rember 1
(rember 2 '(2 3 4))
;(3 4)
(rember 2 '(3 2 4 5))
;(3 4 5)
(rember 2 '(3 2 4 2 5))
;(3 4 2 5)

;;recursively filter arguement out of  all input
(defun rember (x l)
  ( cond
    ( (null l) l)
    ( (eq x (car l))(rember x (cdr l)))
    ( t ( cons (car l) (rember x (cdr l))))
    )
  )
;;demo rember 2
(rember 2 '(2 3 4))
;(3 4)
(rember 2 '(3 2 4 5))
;(3 4 5)
(rember 2 '(3 2 4 2 5))
;(3 4 5)


;;recursively take head of inner lists
(defun firsts (l)
  (cond
   ( (null l)())
   ( t (cons (car (car l))(firsts (cdr l))))
   )
  )
;;demo firsts
(firsts '( (4 5) (6 3)(8 3 1)))
;(4 6 8)

;;replace second param with first param
(defun replace (new old l)
  (cond
   ( (null l) l)
   ( (eq old (car l)) (cons new( cdr l)))
   ( t ( (cons (car l) ( replace new old (cdr l)))))
   )
  )
;;demo replace
(replace 3 6 '(6 5 7))
;(3 5 7)

;;recursion replace all second param with first param
(defun replaceall (new old l)
  (cond
   ( (null l) l)
   ( (eq old (car l)) (cons new (replaceall new old (cdr l))))
   ( t (cons (car l) (replaceall new old (cdr l))))
  )
)
;;demo replaceall
(replaceall 3 6 '(6 5 7 6))
;(3 5 7 3)

;; insert new old etc
(defun insertR (new old l)
  (cond
   ( (null l) l)
   ( (eq old (car l)) (cons (car l) (cons new (cdr l))))
   ( t (cons (car l) (insertR new old (cdr l))))
   )
  )
;;demo insertR
(insertR 3 6 '(6 7 8))
;(6 3 7 8)
(insertR 3 6 '(1 4 6 7 6))
;(1 4 6 3 7 6)

;;insert all occurences
;; insert new old etc
(defun insertallR (new old l)
  (cond
   ( (null l) l)
   ( (eq old (car l)) (cons (car l) (cons new (insertallR new old (cdr l)))))
   ( t (cons (car l) (insertallR new old (cdr l))))
   )
  )
;;demo insertallR
(insertallR 3 6 '(6 7 8))
;(6 3 7 8)
(insertallR 3 6 '(1 4 6 7 6))
;(1 4 6 3 7 6 3)