Flash AS3教程：Direction类和Dot类

}

//更新xy数据
public function updata():void{
if(dis != null){
_x = dis.x;
_y = dis.y;
_r = dis.rotation;
}
}

//计算该点向R方向前进某距离后的点
public function go(num:Number,isChange:Boolean = false):Dot{
updata();
var yx:Number = Math.tan(_r * Math.PI / 180);
var tmpx:Number = num / Math.sqrt(Math.pow(yx,2) 1);
var tmpy:Number = tmpx * yx;
var n:int = Number(Math.abs(_r) <= 90) * 2 - 1;
var dot:Dot = new Dot(_x tmpx * n,_y tmpy * n,_r);
if(isChange){
x = dot.x;
y = dot.y;
}
return dot;
}

//计算该点与另外一点的距离
public function from(_dot:Dot,isQuadrant:Boolean = false):Number{
updata();
var num:Number = Math.sqrt(Math.pow(_dot.x - _x,2) Math.pow(_dot.y - _y,2));
if(!isQuadrant) num = Math.abs(num);
return num;
}

//计算该点与另外一点所形成的线段与水平线的夹角,按顺时间计算
public function angle(_dot:Dot,isRadian:Boolean = false):Number{
updata();
var numx:Number = _dot.x - _x;
var numy:Number = _dot.y - _y;
var num:Number = Math.atan(numy/numx);
if(!isRadian) num = num * 180 / Math.PI;
return num;
}

//返回当前点处在另外一点的哪个象限中 或 返回另外一点处在当前点的哪个象限中
public function quadrant(_dot:Dot,isMaster:Boolean = true):int{
updata();
if(_x == _dot.x || _y == _dot.y){
return 0;
}

var num:int;
var p1:Boolean = (_x - _dot.x) > 0;
var p2:Boolean = (_y - _dot.y) > 0;
num = isMaster ? (p1 ? (p2 ? 2 : 3) : (p2 ? 1 : 4)) : (p1 ? (p2 ? 4 : 1) : (p2 ? 3 : 2));

return num;
}

//返回该点距0点的距离
public function get length():Number{
updata();
var num:Number = Math.sqrt(Math.pow(_x,2) Math.pow(_y,2));
return num;
}

//清除显示对象
public function clear():void{
dis = null;
}

//改变旋转值
public function set r(num:Number):void{
_r = num;
if(dis != null) dis.rotation = num;
if(isListen) dispatchEvent(new DotEvent(DotEvent.R_CHANGE,true));