Function roots

gistfile1.scm

(define (bisection f a b tol)
  (let ((c (* (+ a b) 0.5)))
    (cond ((<= (abs (f c)) tol)  c)
          ((> (* (f a) (f c)) 0) (bisection f c b tol))
          (else                  (bisection f a c tol)))))

(define (newton f fp fb a b tol)
  (let loop ((c (if (> (* (f a) (fb a)) 0) a b)))
    (if (<= (abs (f c)) tol)
        c
        (loop (- c (/ (f c) (fp c)))))))

(define (secant f a b tol)
  (if (<= (abs (f b)) tol)
      b
      (secant f b (- b (* (f b)
                          (/ (- b a)
                             (- (f b) (f a))))))))


;; function bisection(f, a, b, tol) {
;;    var i = 0;
;;    var c = (a+b)/2.0;
;;
;;    while(abs(f(c)) > tol) {
;;        if(f(a) * f(c) > 0) {
;;            a = c;
;;        }
;;        else {
;;            b = c;
;;        }
;;
;;        c = (a + b) / 2.0;
;;        ++i;
;;    }
;;    return (c, i);
;; }