// Compute the intersection of n arrays
Array.prototype.intersect0 =
  function() {
    if (!arguments.length)
    return [];
    var a1 = this;
    var a = a2 = null;
    var n = 0;
    while(n < arguments.length) {
      a = [];
      a2 = arguments[n];
      var l = a1.length;
      var l2 = a2.length;
      for(var i=0; i<l; i++) {
        for(var j=0; j<l2; j++) {
          if (a1[i] === a2[j])
            a.push(a1[i]);
        }
      }
      a1 = a;
      n++;
    }
    //alert(a);
    return a.unique();
  };
  
  
 Array.prototype.intersect =
  function() {
    if (!arguments.length)
    return [];
    var a1 = this;
    var a = a2 = null;
    var n = 0;
    while(n < arguments.length) {
      a = [];
      a2 = arguments[n];
      var l = a1.length;
      var l2 = a2.length;
      for(var i=0; i<l; i++) {
        for(var j=0; j<l2; j++) {
          if (a1[i] === a2[j])
            //a.push(a1[i]);
            a.push(i);
        }
      }
      a1 = a;
      n++;
    }
    //alert(a);
    //return a.unique();
    return a;
  }; 
  
  

// Return new array with duplicate values removed
Array.prototype.unique0 =
  function() {
    var a = [];    
    var l = this.length;
    for(var i=0; i<l; i++) {
      for(var j=i+1; j<l; j++) {
        // If this[i] is found later in the array
        if (this[i] === this[j])
          j = ++i;
      }
      a.push(this[i]);
      
    }
    return a;
  };



Array.prototype.unique = 
function () {
	var r = new Array();
	o:for(var i = 0, n = this.length; i < n; i++)
	{
		for(var x = 0, y = r.length; x < y; x++)
		{
			if(r[x]==this[i])
			{
				continue o;
			}
		}
		r[r.length] = this[i];
	}
	return r;
};


if (!Array.prototype.indexOf)
{
  Array.prototype.indexOf = function(elt /*, from*/)
  {
    var len = this.length;

    var from = Number(arguments[1]) || 0;
    from = (from < 0)
         ? Math.ceil(from)
         : Math.floor(from);
    if (from < 0)
      from += len;

    for (; from < len; from++)
    {
      if (from in this &&
          this[from] === elt)
        return from;
    }
    return -1;
  };
}


function compare(a, b) {
   // psudeo code.
   if (a < b) {
      return -1;
   }
   if (a > b) {
      return 1;
   }
   if (a == b) {
      return 0;
   }
}