/********************************************************************** * $Id: Quadrant.cpp,v 1.2.2.1 2005/05/23 18:41:51 strk Exp $ * * GEOS - Geometry Engine Open Source * http://geos.refractions.net * * Copyright (C) 2001-2002 Vivid Solutions Inc. * * This is free software; you can redistribute and/or modify it under * the terms of the GNU Lesser General Public Licence as published * by the Free Software Foundation.  * See the COPYING file for more information. * ********************************************************************** * $Log: Quadrant.cpp,v $ * Revision 1.2.2.1  2005/05/23 18:41:51  strk * Replaced sprintf uses with ostringstream * * Revision 1.2  2004/07/02 13:28:26  strk * Fixed all #include lines to reflect headers layout change. * Added client application build tips in README. * * Revision 1.1  2004/03/19 09:48:45  ybychkov * "geomgraph" and "geomgraph/indexl" upgraded to JTS 1.4 * * Revision 1.10  2003/11/07 01:23:42  pramsey * Add standard CVS headers licence notices and copyrights to all cpp and h * files. * * **********************************************************************/#include <sstream>#include <geos/geomgraph.h>namespace geos {/*** Returns the quadrant of a directed line segment (specified as x and y* displacements, which cannot both be 0).*/int Quadrant::quadrant(double dx, double dy) {	if (dx == 0.0 && dy == 0.0) {		ostringstream s;		s<<"Cannot compute the quadrant for point ";		s<<"("<<dx<<","<<dy<<")"<<endl;		throw new IllegalArgumentException(s.str());	}	if (dx >= 0) {		if (dy >= 0)			return 0;		else			return 3;	} else {		if (dy >= 0)			return 1;		else		return 2;	}}/*** Returns the quadrant of a directed line segment from p0 to p1.*/int Quadrant::quadrant(const Coordinate& p0, const Coordinate& p1) {	double dx=p1.x-p0.x;	double dy=p1.y-p0.y;	if (dx==0.0 && dy==0.0)		throw new IllegalArgumentException("Cannot compute the quadrant for two identical points " + p0.toString());	return quadrant(dx, dy);}/*** Returns true if the quadrants are 1 and 3, or 2 and 4*/bool Quadrant::isOpposite(int quad1, int quad2){	if (quad1==quad2) return false;	int diff=(quad1-quad2+4)%4;	// if quadrants are not adjacent, they are opposite	if (diff==2) return true;	return false;}/** * Returns the right-hand quadrant of the halfplane defined by the two quadrants,* or -1 if the quadrants are opposite, or the quadrant if they are identical.*/int Quadrant::commonHalfPlane(int quad1, int quad2){	// if quadrants are the same they do not determine a unique common halfplane.	// Simply return one of the two possibilities	if (quad1==quad2) return quad1;	int diff=(quad1-quad2+4)%4;	// if quadrants are not adjacent, they do not share a common halfplane	if (diff==2) return -1;	//	int min=(quad1<quad2)? quad1:quad2;	int max=(quad1>quad2)? quad1:quad2;	// for this one case, the righthand plane is NOT the minimum index;	if (min==0 && max==3) return 3;	// in general, the halfplane index is the minimum of the two adjacent quadrants	return min;}/*** Returns whether the given quadrant lies within the given halfplane (specified* by its right-hand quadrant).*/bool Quadrant::isInHalfPlane(int quad, int halfPlane){	if (halfPlane==3) {		return quad==3 || quad==0;	}	return quad==halfPlane || quad==halfPlane+1;}/*** Returns true if the given quadrant is 0 or 1.*/bool Quadrant::isNorthern(int quad) {	return quad==0 || quad==1;}}