#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;

double f(double x) {
    return exp(-x)-x;
} //functia definita

int main() {
    cout.precision(6);
    cout.setf(ios::fixed);
    double x, x00, x0, errmax, err, errrel, err0;
    int it, itmax;
    cout << "Insert the initial values x00, x0 = "; cin>>x00>>x0;
    cout << "The maximum error errmax="; cin >> errmax;
    cout << "Insert the max iter. no. itmax="; cin >> itmax;
    err = 1; it = 0;
    x = x0-f(x0)*(x0-x00) / (f(x0)-f(x00));
    cout << "\n------------------------DISPLAY RESULTS---------- -\n\n";
    cout << "\n"<<setw(4)<<"It"<<setw(12)<<"x"<<setw(12) << "err" <<setw(12) << "x00" << setw(12) << "x0"<< setw(12) << "err0" << setw(12) << "errrel"<< setw(12) << "f";
    cout << "\n-- ---------------------------------\n";
    while (err > errmax && it <= itmax) {
        it++;
        x = x0 - f(x0)*(x0 - x00) / (f(x0) - f(x00));
        err = fabs(x - x0);
        errrel = fabs((x - x0) / x0);
        err0 = fabs(f(x));
        cout << setw(4) << it << setw(12) << x << setw(12) << err << setw(12) << x00 << setw(12) << x0 << setw(12) << err0 << setw(12) << errrel << setw(12) << f(x) << endl;
        x00 = x0; //a egalat cu b pentru decalare interval
        x0 = x; //b egalat cu ultimul c calculat
        if (f(x) == 0) break;
    }
    if((err <= errmax && it <= itmax) || (f(x) == 0)) {
        cout << "\n\n"<<"The solution converges after "<<it<< " iterations:\n";
        cout << endl << "The solution is x=" << x << endl;
    }
 else {

 cout << "\n\n"<<"The sol.does not converges after " << it << " iterations.\n";
 cout << "The partial value at the imposed max. no. of iters. is x=" << x << "\n";
    }

}