function - change - to + in Common Lisp -

function - change - to + in Common Lisp -

is there way alter - (minus) function + (plus) function?

my homework implement sin calculation on macluaurin series

sin(x) = x-(x^3/3!)+(x^5/5!) -(x^7/7!)+(x^9/9!)-...

each article has different sign. lisp code

(defun sinmac (x series n plusminus) (cond ((= series 0) 0) (t (funcall plusminus (/ (power x n) (factorial n)) (sinmac x (- series 1) (+ n 2) plusminus)))))

is possible alter plusminus exchange sign? if '+ function send '- next recursive call. phone call (got '-) phone call '+ , on...

you circular list. so:

(defun sin-mac (x series n plus-minus) (cond ((zerop series) 0) (t (funcall (car plus-minus) (/ (power x n) (factorial n)) (sin-mac x (1- series) (+ n 2) (cdr plus-minus)))))) (sin-mac x series 1 '#0=(+ - . #0#))

or better, wrap initial arguments using labels:

(defun sin-mac (x series) (labels ((recur (series n plus-minus) (cond ((zerop series) 0) (t (funcall (car plus-minus) (/ (power x n) (factorial n)) (recur (1- series) (+ n 2) (cdr plus-minus))))))) (recur series 1 '#0=(+ - . #0#))))

function lisp common-lisp