function ImagePair( ms, tns )
{
	this._mainSrc = ms;
	this._thumbnailSrc = tns;
	
	this.getMainSrc = function()
	{
		return this._mainSrc;
	}
	
	this.getThumbnailSrc = function()
	{
		return this._thumbnailSrc;
	}
}

var imageNameArray = new Array();
imageNameArray[0] = "tn1";
imageNameArray[1] = "tn2";
imageNameArray[2] = "main";
var imageIndexArray = new Array();
imageIndexArray[0] = 0;
imageIndexArray[1] = 1;
imageIndexArray[2] = 2;
var imageDataArray = new Array(); // initialised in including file


/* Swap the main image with the fuller version of the
 *  one in thumbnail n where n equals 0 or 1
 *  this will do the rollover magic
 */
function swap( n )
{
		var tmp = imageIndexArray[2];
		imageIndexArray[2] = imageIndexArray[n];
		imageIndexArray[n] = tmp;
		//window.status = "index array: " + imageIndexArray.join(",");
		//alert("Swapping " + imageNameArray[n] + " with " + imageNameArray[2] );
		//alert(document.images[imageNameArray[0]].src);
		document.images[ imageNameArray[n] ].src = imageDataArray[ imageIndexArray[n] ].getThumbnailSrc();
		document.images[ imageNameArray[2] ].src = imageDataArray[ imageIndexArray[2] ].getMainSrc();
		
}