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

int deriv(double, int, double *, double *, void *);

/*------------------------------------------------------------------------------
  Main routine to test Runge-Kutta integrator.
*/
int main(int argc, char *argv[])
{
    int istep, nstep, ny;
    double x0, x1;
    double *y0, *y1;

    /* length of y vector */
    ny = 1;

    y0 = malloc(ny * sizeof(double));
    y1 = malloc(ny * sizeof(double));
    
    <your code>

    /* loop calls to RK routine */
    for (istep = 0; istep < nstep; istep++) {
	    
	<your code>

	/* Runge-Kutta step */
	rk4(&deriv, x0, x1, ny, y0, y1, 0x0);

        <your code>
    }

    return(0);
}

/*------------------------------------------------------------------------------
  dydx = - y
*/
int deriv(double x, int ny, double *y, double *dydx, void *pass)
{
    <your code>
}