Determining if object is within defined area.

integer l = polygon != []; 
//-- same as
integer L = llGetListLength( polygon );
//-- the action is (list_a_length - list_b_length) and it only works for lists


inPoly = !inPoly;
//-- same as
if (TRUE == inPoly){
 inPoly = FALSE;
}else{
  inPoly = TRUE;
}
//-- basic boolean switch

return inPoly != 0;
//-- same as
if (FALSE == inPoly){
  return FALSE;
}else{
  return TRUE;
}
//-- returns the boolean truth of the statement... probably to limit inPoly to being
//-- either [0 or 1] instead of [0 or any_non-zero_number] (the test forces boolean
//-- returns, !(!inPoly) might be faster, not sure.. definitely confusing that way though,
//-- and very non-standard, the shown method is standard practice)

integer uPointInPolygon2D( list vLstPolygon, vector vPosTesting ){
	integer vBooInPlygn;
	integer vIntCounter = [] != vLstPolygon;
	vector  vPosVertexA = llList2Vector( vLstPolygon, vIntCounter );
	vector  vPosVertexB;
	
	while (vIntCounter){
		vPosVertexB = vPosVertexA;
		vPosVertexA = llList2Vector( vLstPolygon, ++vIntCounter );
		
		if ((vPosVertexA.y > vPosTesting.y) ^ (vPosVertexB.y > vPosTesting.y)){
			if (vPosTesting.x < (vPosVertexB.x - vPosVertexA.x) *
			                    `(vPosTesting.y - vPosVertexA.y) / 
			                    `(vPosVertexB.y - vPosVertexA.y) +  vPosVertexA.x ){
				vBooInPlygn = !vBooInPlygn;
			}
		}
	}
	return vBooInPlygn;
}

integer uPointInPolygon2D_XY( list vLstPolygonXY,
                              `float vFltTesting_X,
                              `float vFltTesting_Y ){
	integer vBooInPlygnXY;
	integer vIntCounterXY = ([] != vLstPolygonXY);
	float   vFltVertexA_X = llList2Float( vLstPolygonXY, -2 );
	float   vFltVertexA_Y = llList2Float( vLstPolygonXY, -1 );
	float   vFltVertexB_X;
	float   vFltVertexB_Y;
	
	while (vIntCounterXY){
		vFltVertexB_X = vFltVertexA_X;
		vFltVertexB_Y = vFltVertexA_Y;
		vFltVertexA_X = llList2Float( vLstPolygonXY, vIntCounterXY++ );
		vFltVertexA_Y = llList2Float( vLstPolygonXY, vIntCounterXY++ );
		
		if ((vFltVertexA_Y > vFltTesting_Y) ^ (vFltVertexB_Y > vFltTesting_Y)){
			if (vFltTesting_X < (vFltVertexB_X - vFltVertexA_X) *
			                    `(vFltTesting_Y - vFltVertexA_Y) / 
			                    `(vFltVertexB_Y - vFltVertexA_Y) +  vFltVertexA_X ){
				vBooInPlygnXY = !vBooInPlygnXY;
			}
		}
	}
	return vBooInPlygnXY;
}
	/*//-- LSL Port 2009 Void Singer --//*/
	/*//-- Copyright (c) 1970-2003, Wm. Randolph Franklin	--//*/
/*
Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimers.
2. Redistributions in binary form must reproduce the above copyright notice
   in the documentation and/or other materials provided with the distribution.
3. The name of W. Randolph Franklin may not be used to endorse or promote
   products derived from this Software without specific prior written permission

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE. 
*/

integer uPointInPolygon2D( list vLstPolygon, vector vPosTesting ){
	integer vBooInPlygn;
	 //-- ([] != vLstPolygon) is equivalent to
	 //-- llGetListLength( [] ) - llGetListLength( vLstPolygon )
	integer vIntCounter = ([] != vLstPolygon);
	vector  vPosVertexA = llList2Vector( vLstPolygon, vIntCounter );
	vector  vPosVertexB;
	
	while (vIntCounter){
		vPosVertexB = vPosVertexA;
		vPosVertexA = llList2Vector( vLstPolygon, ++vIntCounter );
		
		 //-- ((A.y > T.y) ^ (B.y > T.y)) == ((A.y > T.y) - (T.y < B.y)) 
		if ((vPosVertexA.y > vPosTesting.y) ^ (vPosVertexB.y > vPosTesting.y)){
			 //-- only test this if the above is TRUE, avoids possible Divide by zero
			if (vPosTesting.x < (vPosVertexB.x - vPosVertexA.x) *
			                    `(vPosTesting.y - vPosVertexA.y) / 
			                    `(vPosVertexB.y - vPosVertexA.y) +  vPosVertexA.x ){
				 //-- Reverse the boolean state
				vBooInPlygn = !vBooInPlygn;
			}
		}
	}
	return vBooInPlygn;
}

integer uPointInPolygon2D_XY( list vLstPolygonXY,
                              `float vFltTesting_X,
                              `float vFltTesting_Y ){
	integer vBooInPlygnXY;
	 //-- ([] != vLstPolygon) is equivalent to
	 //-- llGetListLength( [] ) - llGetListLength( vLstPolygon )
	integer vIntCounterXY = ([] != vLstPolygonXY);
	float   vFltVertexA_X = llList2Float( vLstPolygonXY, -2 );
	float   vFltVertexA_Y = llList2Float( vLstPolygonXY, -1 );
	float   vFltVertexB_X;
	float   vFltVertexB_Y;
	
	while (vIntCounterXY){
		vFltVertexB_X = vFltVertexA_X;
		vFltVertexB_Y = vFltVertexA_Y;
		vFltVertexA_X = llList2Float( vLstPolygonXY, vIntCounterXY++ );
		vFltVertexA_Y = llList2Float( vLstPolygonXY, vIntCounterXY++ );
		
		 //-- ((A.y > T.y) ^ (B.y > T.y)) == ((A.y > T.y) - (T.y < B.y)) 
		if ((vFltVertexA_Y > vFltTesting_Y) ^ (vFltVertexB_Y > vFltTesting_Y)){
			 //-- only test this if the above is TRUE, avoids possible Divide by zero
			if (vFltTesting_X < (vFltVertexB_X - vFltVertexA_X) *
			                    `(vFltTesting_Y - vFltVertexA_Y) / 
			                    `(vFltVertexB_Y - vFltVertexA_Y) +  vFltVertexA_X ){
				 //-- Reverse the boolean state
				vBooInPlygnXY = !vBooInPlygnXY;
			}
		}
	}
	return vBooInPlygnXY;
}
	/*//-- LSL Port 2009 Void Singer --//*/
	/*//-- Copyright (c) 1970-2003, Wm. Randolph Franklin	--//*/
/*
Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimers.
2. Redistributions in binary form must reproduce the above copyright notice
   in the documentation and/or other materials provided with the distribution.
3. The name of W. Randolph Franklin may not be used to endorse or promote
   products derived from this Software without specific prior written permission

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE. 
*/