Second Order Runge Kutta Method

#include <iostream>
#include <cstdlib>

using namespace std;

class RungeSecondOrder{
        double x0, y0, h, no_of_intervals;
    public:
        RungeSecondOrder(double = 0, double = 0, double = 0, int = 0);
        double f(double, double);
        double calcY(double, double);
        double displayAll();
};

inline double RungeSecondOrder::f(double x, double y){
    return y + (0 * x);
}

inline RungeSecondOrder::RungeSecondOrder(double h, double x0, double y0, int no_of_intervals){
    RungeSecondOrder::h = h;
    RungeSecondOrder::x0 = x0;
    RungeSecondOrder::y0 = y0;
    RungeSecondOrder::no_of_intervals = no_of_intervals;
}

inline double RungeSecondOrder::calcY(double x, double y){
    double k1 = h * f(x, y);
    double k2 = h * f(x + h, y + h);
    return y + (.5 * (k1 + k2));
}

double RungeSecondOrder::displayAll(){
    double curr_x = x0, curr_y = y0;
    cout << "x = " << curr_x << " y = " << curr_y << endl;
    for(double i = 1; i <= no_of_intervals; i++){
        curr_y = calcY(curr_x, curr_y);
        curr_x += h;
        cout << "x = " << curr_x << " y = " << curr_y << endl;
    }
}

int main() {
    system("cls");
    double x0, y0, h, no_of_intervals;
    cout << "Enter x0 = ";
    cin >> x0;
    cout << "Enter y0 = ";
    cin >> y0;
    cout << "Enter h = ";
    cin >> h;
    cout << "Enter number of intervals = ";
    cin >> no_of_intervals;
    RungeSecondOrder obj(h, x0, y0, no_of_intervals);
    obj.displayAll();
    cin.ignore();
    cin.get();
    return 0;
}