double
log_stadnorm_density (double x)
{
	        /* log-Normal(0,1) density, x in R */
	                return -0.91893853 -0.5*x*x;
}



double
log_norm_density (double x, double my, double sigma2)
{
       /* log-Normal(my, sigma2) density, my in R, sigma > 0, x in R */
       double sigma;
       sigma = sqrt(sigma2);
       return -log(sigma) + log_stadnorm_density((x-my)/sigma);
}



double
gammln (double xx)
{
	double x, tmp, ser;
	static double cof[6] =
	   	{76.18009173, -86.50532033, 24.01409822,
	         -1.231739516, 0.120858003e-2, -0.536382e-5};
	int j;
	            
	x = xx - 1.0;
	tmp = x + 5.5;
	tmp -= (x + 0.5) * log (tmp);
	ser = 1.0;
	for (j = 0; j <= 5; j++)
	{
	      	x += 1.0;
	        ser += cof[j] / x;
	}
	return -tmp + log (2.50662827465 * ser);
}
 
 
double
log_gamma_density (double x, double alpha, double lambda)
{
 return (alpha*log(lambda)+(alpha-1)*log(x)-lambda*x-gammln (alpha));
}