function [res,iter,y]=fnewton(func,dfunc,x0,tol)

% func is the name of an m-file (in single quotes) which is the function
% for which we are trying to find a zero.
% dfunc is the name of a m-file which contains the derivative of func.
% x0 is the initial geuss at a root.
% tol is the tolerance to compute x within.

% res is the result, the approximation to the root
% iter is the number of iterations taken

iter=0;
x=x0;
% y(1)=x;
d=feval(func,x)/feval(dfunc,x);
while abs(d)>tol
    iter=iter+1;
    x=x-d;
    % y(iter+1)=x;
    d=feval(func,x)/feval(dfunc,x);
end
res=x;