1rBY6H - Online C++0x Compiler & Debugging Tool

#include <bits/stdc++.h>
using namespace std;

// Modified function name
double customFunc(double val) {
    return (2.0 * val * val * val + 3.0 * val - 1.0);
}

int main() {
    double left, right, midpoint, f_left, f_right, f_mid, tolerance = 0.0001, root;
    int iteration = 0;

    // Input loop instead of goto
    while (true) {
        cout << "Enter two initial guesses: ";
        cin >> left >> right;

        f_left = customFunc(left);
        f_right = customFunc(right);

        if (f_left * f_right < 0) {
            break;
        } else {
            cout << "Invalid interval. Try again.\n";
        }
    }

    // First midpoint calculation
    midpoint = (left + right) / 2.0;
    f_mid = customFunc(midpoint);

    if (f_mid == 0) {
        cout << fixed << setprecision(8);
        cout << "Exact root found: " << midpoint << endl;
        return 0;
    }

    // Header for output
    cout << "Iter\tMidpoint\tLeft\tRight\tf(Mid)\tf(Left)\tf(Right)\n";
    cout << iteration << "\t" << fixed << setprecision(8) << midpoint << "\t"
         << left << "\t" << right << "\t"
         << f_mid << "\t" << f_left << "\t" << f_right << endl;

    while (true) {
        midpoint = (left + right) / 2.0;
        f_mid = customFunc(midpoint);
        iteration++;

        cout << iteration << "\t" << fixed << setprecision(8) << midpoint << "\t"
             << left << "\t" << right << "\t"
             << f_mid << "\t" << f_left << "\t" << f_right << endl;

        if (fabs((right - left) / right) < tolerance || iteration > 8) {
            break;
        }

        if (f_left * f_mid < 0) {
            right = midpoint;
            f_right = f_mid;
        } else {
            left = midpoint;
            f_left = f_mid;
        }

        root = midpoint;
    }

    cout << fixed << setprecision(8) << "Approximate root = " << root << endl;
    return 0;
}