//给Array数组对象增加一个功能（使用类功能）---------------------------------------------

//----- 乱序算法对象 -----//
function rand()
{
var i=0;
var l=this.length;
var dl=l/2;
if(l>0) while(i<dl) 
{
num1 = random(l);
num2 = random(l);
temp = this[num1];
this[num1] = this[num2];
this[num2] = temp;
i = i+1;
}
}
Array.prototype.rand = rand;

//两点所成角度---------------------------------------------

// Get the angle between two points. （得到两点之间的角度）
function getAngle(px1, py1, px2, py2) {
	x = px2-px1;
	y = py2-py1;
	hyp = Math.sqrt(Math.pow(x, 2)+Math.pow(y, 2));
	cos = x/hyp;
	rad = Math.acos(cos);
	// Ask your math teacher if you don’t understand this one.（如果你看不懂，就去问你的数学老师）
	deg = 180/(Math.PI/rad);
	// Yes, we do got one angle, rad, by 'Math.acos(cos)', but in radians.（是的，我们通过cos得到了一个角度“rad”，不过是以弧度为单位的）
	// Therefore, we need do one more step to transfer it to normal angle we need.（因此，我们需要再进一步把它转换成我们所需要的标准的角度）
	if (y<0) {
		deg = -deg;
	} else if ((y == 0) && (x<0)) {
		deg = 180;
	}
	return deg;
}

//两点间距离---------------------------------------------

// Get the distance between two points. (得到两点之间的距离)
function getDist(px1, py1, px2, py2) {
	x = px2-px1;
	y = py2-py1;
	hyp = Math.sqrt(Math.pow(x, 2)+Math.pow(y, 2));
	return hyp;
}

//缓冲运动---------------------------------------------

//针对一个物体和一个点之间的缓冲运动
function buffer(obj_mc, speed, x, y) {
	this[obj_mc].onEnterFrame = function() {
		this._x += (x-this._x)/speed;
		this._y += (y-this._y)/speed;
	};
}
this.onMouseDown = function() {
	buffer("rec", 2, _xmouse, _ymouse);
};