#include <stdio.h>
#include <math.h>

#define x0 2

#define v0 1

#define t0 0
#define tf 100

#define w02 3

#define dt 1e-2
#define N ((tf-t0)/dt)

double dvdt(double x, double v, double t)
{
	return -w02*x;
}

int main(void)
{
	double x = x0, xn, 
	       t = t0, tn, 
	       v = v0, vn;
	int i;

	FILE *h = fopen("./euler.dat","w+");

	for (i = 0; i < N; ++i)
	{
		xn  = x + v*dt;
		vn = v + dvdt(x,v,t)*dt;
		tn = t + dt;

		fprintf(h, "%d %f %f\n", i, t, x);

		x = xn;
		v = vn;
		t = tn;
	}

	fclose(h);
	return 0;
}