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

struct place {
	double	ladeg, lamin;
	double	lodeg, lomin;
	char	*city, *country;
} Place[] = {
	/* Eight places which form roughly a cube */
	-12, -30, -96, -50, "Cocos (Keeling) Islands", "",
	12, 24, 83, 40, "Punta Peclas", "NICARAGUA",
	-56, -15, 68, 42, "Cape Horn", "CHILE",
	57, 41, -114, 0, "Bodaybo", "RUSSIA",
	42, 20, 8, 45, "Vigo", "SPAIN",
	-21, -38, -21, -25, "Ghanzi", "BOTSWANA",
	21, 20, 157, 55, "Honolulu", "USA",
	-43, -32, -172, -37, "Christchurch", "NEW ZEALAND",
};

/*
 * This program is based on one by david.williams at ablelink.org
 * Translated from Basic to C by jda, who also eliminated
 * some frills.
 */
#define	J_PI  3.1415926535898

double	degmin2rad(double deg, double min)
{
	return (deg + min / 60.0) * J_PI / 180;
}

/* We use only an average Earth radius for calculations */
double Radnet = 6371;	/* Earth radius in km */
/*
 * double Radpolar = 6356.9;
 * double Radequat = 6378.5;
 */

/* Calculate distance between long1, lat1, long2, lat2 */
double getdist(double long1, double lat1, double long2, double lat2)
{
	double	lg, y, t, x, z, r, a2;

	lg = long2 - long1;
	y = sin(lat1);
	t = cos(lat1);
	x = t * sin(lg);
	z = t * cos(lg);
	r = sqrt(y*y + z*z);
	a2 = cos(atan2(y, z) - lat2);
	y = - r * a2;
	return Radnet * (J_PI / 2 + atan2(y, sqrt(1 - y*y)));
}

/* Calculate distance between two places */
double getd2(int ix1, int ix2)
{
	double long1, lat1, long2, lat2;

	long1 = degmin2rad(Place[ix1].lodeg, Place[ix1].lomin);
	lat1 = degmin2rad(Place[ix1].ladeg, Place[ix1].lamin);
	long2 = degmin2rad(Place[ix2].lodeg, Place[ix2].lomin);
	lat2 = degmin2rad(Place[ix2].ladeg, Place[ix2].lamin);
	return getdist(long1, lat1, long2, lat2);
}

int main(int argc, char **argv)
{
	int	ix1, ix2;

	for (ix1 = 0; ix1 < sizeof(Place)/sizeof(*Place); ix1++)
	for (ix2 = ix1 + 1; ix2 < sizeof(Place)/sizeof(*Place); ix2++)
		printf(" %8.1f is Distance from %s (%s) to %s (%s)\n",
			getd2(ix1, ix2),
			Place[ix1].city, Place[ix1].country,
			Place[ix2].city, Place[ix2].country);
	exit(0);
}