function [a,b,fail] = bisect(f,a,b,eps,N) 
% it is assumed that either f(a)>0 and f(b)<0
% or f(a)<0 and f(b)>0.
%p.158
for i=1:N
    m = (a+b)/2;
    fm = feval(f,m);
    if fm*feval(f,a)<0
        b = m;
    else a = m;
    end;
    fprintf('The root is in the interval [%f,%f]\nm=%f, f(m)=%f\n', a,b,m,fm);
    if (abs(fm)<eps) | ((b-a)<eps)
        fail = 0;
        fprintf('Succeded after %i steps', i);
        return;
    end
end
fprintf('Failed after %i steps', N);
fail = 1;