function [k,p,err,P]=fixpt(g,p0,tol,max1)
%Input-g is the iteration function input as a string 'g'
%     -p0 is the initial guess for the fixed point
%     -tol is the tolerance
%     -max1 is the maximum number of iterations
%Output-k is the number of iterations that were carried out
%      -p is the approximation to the fixed point
%      -err is the error in the approximation 
%      -P contains the sequencee{pn}用于計算不動點的迭代問題
P(1)=p0;
for k=2:max1;
    P(k)=feval('g',P(k-1));
    err=abs(P(k)-P(k-1));
    relerr=err/(abs(P(k))+eps);
    p=P(k);
    if (err<tol)|(relerr<tol),fprintf('%f',p);
        break;
    end
end
if k==max1
    disp('maximum number of iterations exceeded')
end
P=P';