package rk4;

public abstract class RungeKutta {
    public void resolver(double tf, Estado e, double h){
//variables auxiliares
	    double k1, k2, k3, k4;
	    double l1, l2, l3, l4;
	    double q1, q2, q3, q4;
	    double m1, m2, m3, m4;
//condiciones iniciales
	    double x=e.x;
	    double y=e.y;
	    double vx=e.vx;
	    double vy=e.vy;
	    double t0=e.t;

	    for(double t=t0; t<tf; t+=h){
		    k1=h*vx;
		    l1=h*f(x, y, vx, vy, t);
		    q1=h*vy;
		    m1=h*g(x, y, vx, vy, t);

		    k2=h*(vx+l1/2);
		    l2=h*f(x+k1/2, y+q1/2, vx+l1/2, vy+m1/2, t+h/2);
		    q2=h*(vy+m1/2);
		    m2=h*g(x+k1/2, y+q1/2, vx+l1/2, vy+m1/2, t+h/2);

		    k3=h*(vx+l2/2);
		    l3=h*f(x+k2/2, y+q2/2, vx+l2/2, vy+m2/2, t+h/2);
		    q3=h*(vy+m2/2);
		    m3=h*g(x+k2/2, y+q2/2, vx+l2/2, vy+m2/2, t+h/2);

		    k4=h*(vx+l3);
		    l4=h*f(x+k3, y+q3, vx+l3, vy+m3, t+h);
		    q4=h*(vy+m3);
		    m4=h*g(x+k3, y+q3, vx+l3, vy+m3, t+h);
//nuevo estado del sistema
		    x+=(k1+2*k2+2*k3+k4)/6;
		    vx+=(l1+2*l2+2*l3+l4)/6;
		    y+=(q1+2*q2+2*q3+q4)/6;
		    vy+=(m1+2*m2+2*m3+m4)/6;
	    }
//cambia el estado de la partícula
	    e.x=x;
	    e.y=y;
	    e.vx=vx;
	    e.vy=vy;
	    e.t=tf;
    }
    abstract public double f(double x, double y, double vx, double vy, double t);
    abstract public double g(double x, double y, double vx, double vy, double t);

}