typedef Xywh = {x:Float, y:Float, width:Float, height:Float};

using PlaceTools;

class PlaceTools
{
    public static var HORIZONTAL:String = "horizontal";

    public static function rightOf(target:Xywh, ref:Xywh, ?padding:Int=0, ?align:Bool=true, ?width:Float=0, ?height:Float=0):Void
    {
        target.x = ref.x + ref.width + padding;
        if(align) target.y = ref.y;
        if(width!=0)target.width=width;
        if(height!=0)target.height=height;
    }
    public static function distribute(arr:Array<Xywh>, ?padding:Int=0, ?dtype:String="horizontal")
    {
        for(i in 1...arr.length)
        {
            switch(dtype)
            {
                case HORIZONTAL: arr[i].rightOf(arr[i-1], padding);
                default: trace(not implemented in this example);
            }
        }
    }
}

//------------------------------------
//var btn1 = new MyButton(); //extends Sprite
[btn1, btn2, btn3].distribute(20, PlaceTools.HORIZONTAL);

//Compiler error: Array<MyButton> has no field distribute

//changing
public static function distribute(arr:Array<Xywh>, ?padding:Int=0, ?dtype:String="horizontal")
//into:
public static function distribute(arr:Array<Dynamic>, ?padding:Int=0, ?dtype:String="horizontal")
//runtime error : btn1 has no field rightOf