function call_when_loaded(func){
    var oldonload = window.onload;
    if (typeof window.onload != 'function') {
      window.onload = func;
    }else {
      window.onload = function() {
        if (oldonload) {
	      oldonload();
        }
        func();
      }
    }
  }

function add_event_to_element(element, event_type, func, use_capture) {
  if (element.addEventListener) {
	element.addEventListener(event_type, func, use_capture);
	return true;
  }
  else if (element.attachEvent) {
	return element.attachEvent('on' + event_type, func);
  }
  else {
	element['on' + event_type] = func;
  }
}

function change_class_of_element(element, class_name){
  element.className = class_name;	
}

function give_id_to_element(element, id){
  if(!element.id){
    element.id = id;
  }	
}

Array.prototype.swap=function(a, b){
  var tmp=this[a];
  this[a]=this[b];
  this[b]=tmp;
}