判断点在线段的左右侧

privatestring funReturnRightOrLeft(IPoint poiA,IPoint poiB,IPoint poiM)

{

    stringstrResult = "";

    doubleax = poiB.X - poiA.X;

    doubleay = poiB.Y - poiA.Y;

    doublebx = poiM.X - poiA.X;

    doubleby = poiM.Y - poiA.Y;

    doublejudge = ax * by - ay * bx;

    if(judge>0)

    {

        strResult="LEFT";

    }

    elseif(judge<0)

    {

        strResult = "RIGHT";

    }

    else

    {

        strResult = "ONTHELINE";

    }

    returnstrResult;

}