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/* Functions using doubles */

double d_diameter, d_lat_1, d_lon_1;
double d_cos_lat_1;

void SetUpDistance_double(double new_diameter, double new_lat_1, double new_lon_1) {
	d_diameter = new_diameter;
	d_lat_1 = new_lat_1;
	d_lon_1 = new_lon_1;
	d_cos_lat_1 = cos( new_lat_1 );
}

double HaversineDistance_double(double lat_0, double lon_0) {
	double sin_lat_diff_over_2 = sin( ( lat_0 - d_lat_1 ) / 2.0 );
	double sin_lon_diff_over_2 = sin( ( lon_0 - d_lon_1 ) / 2.0 );
	
	double n = ( sin_lat_diff_over_2 * sin_lat_diff_over_2 ) 
	          + (
	              ( sin_lon_diff_over_2 * sin_lon_diff_over_2 )
	              * d_cos_lat_1
	              * cos( lat_0 )
	            );
	
	/* The haversine formula may get messy around antipodal points so clip to the largest sane value. */
	if ( n < 0.0 ) { n = 0.0; }
	
	return d_diameter  * asin( sqrt(n) );
}

/* End of C code */

MODULE = Geo::Index  PACKAGE = Geo::Index  

PROTOTYPES: DISABLE


unsigned int
GetCCodeVersion ()

unsigned int
fast_log2_double (n)
	double	n

unsigned int
fast_log2_float (n)
	float	n

void
ComputeAreaExtrema_float (tile_adjust, max_size, max_level, p_lat, p_lat_rad, p_lon, polar_circumference, search_radius)
	int	tile_adjust
	unsigned long	max_size
	unsigned int	max_level
	float	p_lat
	float	p_lat_rad
	float	p_lon
	float	polar_circumference
	float	search_radius
        PREINIT:
        I32* temp;
        PPCODE:
        temp = PL_markstack_ptr++;
        ComputeAreaExtrema_float(tile_adjust, max_size, max_level, p_lat, p_lat_rad, p_lon, polar_circumference, search_radius);
        if (PL_markstack_ptr != temp) {
          /* truly void, because dXSARGS not invoked */
          PL_markstack_ptr = temp;
          XSRETURN_EMPTY; /* return empty stack */
        }
        /* must have used dXSARGS; list context implied */
        return; /* assume stack size is correct */

void
ComputeAreaExtrema_double (tile_adjust, max_size, max_level, p_lat, p_lat_rad, p_lon, polar_circumference, search_radius)
	int	tile_adjust
	unsigned long	max_size
	unsigned int	max_level
	double	p_lat
	double	p_lat_rad
	double	p_lon
	double	polar_circumference
	double	search_radius
        PREINIT:
        I32* temp;
        PPCODE:
        temp = PL_markstack_ptr++;
        ComputeAreaExtrema_double(tile_adjust, max_size, max_level, p_lat, p_lat_rad, p_lon, polar_circumference, search_radius);
        if (PL_markstack_ptr != temp) {
          /* truly void, because dXSARGS not invoked */
          PL_markstack_ptr = temp;
          XSRETURN_EMPTY; /* return empty stack */
        }
        /* must have used dXSARGS; list context implied */
        return; /* assume stack size is correct */

void
SetUpDistance_float (new_diameter, new_lat_1, new_lon_1)
	float	new_diameter
	float	new_lat_1
	float	new_lon_1
        PREINIT:
        I32* temp;
        PPCODE:
        temp = PL_markstack_ptr++;
        SetUpDistance_float(new_diameter, new_lat_1, new_lon_1);
        if (PL_markstack_ptr != temp) {
          /* truly void, because dXSARGS not invoked */
          PL_markstack_ptr = temp;
          XSRETURN_EMPTY; /* return empty stack */
        }
        /* must have used dXSARGS; list context implied */
        return; /* assume stack size is correct */

float
HaversineDistance_float (lat_0, lon_0)
	float	lat_0
	float	lon_0

void
SetUpDistance_double (new_diameter, new_lat_1, new_lon_1)
	double	new_diameter
	double	new_lat_1
	double	new_lon_1
        PREINIT:
        I32* temp;
        PPCODE:
        temp = PL_markstack_ptr++;
        SetUpDistance_double(new_diameter, new_lat_1, new_lon_1);
        if (PL_markstack_ptr != temp) {
          /* truly void, because dXSARGS not invoked */
          PL_markstack_ptr = temp;
          XSRETURN_EMPTY; /* return empty stack */
        }
        /* must have used dXSARGS; list context implied */
        return; /* assume stack size is correct */

double
HaversineDistance_double (lat_0, lon_0)
	double	lat_0
	double	lon_0