#include <stdlib.h>
#include "rk4.h"

/*------------------------------------------------------------------------------
  One step of 4th order Runge-Kutta integrator.

  Integrates a set of ny equations
  dy
  -- = f[x, y]
  dx
  from x0 to x1.
*/
int rk4(derivf deriv, double x0, double x1, int ny, double *y0, double *y1, void *pass)
{
    double dx;
    double *f0, *f1, *f2, *f3;

    f0 = (double *) malloc(ny * sizeof(double));
    f1 = (double *) malloc(ny * sizeof(double));
    f2 = (double *) malloc(ny * sizeof(double));
    f3 = (double *) malloc(ny * sizeof(double));

    dx = x1 - x0;

    <your code>

    free(f0);
    free(f1);
    free(f2);
    free(f3);
}