var expand_ul = function(el) {
	el.className = 'new';
};

var shrink_ul = function(el) {
	el.className = 'shrunk';
};

function scopepreserver(n,arr) {
	return function () {
		expand_ul(arr[n][1]);
		for (var i=0; i < arr.length; i++)
		{
			if (i != n) shrink_ul(arr[i][1]);
		}
		return false;
	}; 
};

var getPairedArray = function(el) {
	var arr = el.childNodes;
	var pairs = [];
	
	for (var i =0; i < arr.length; i++)
	{
		if (arr[i].nodeType == 1) 
		{
			if (arr[i].getElementsByTagName('ul').length)
			{
				var ul = arr[i].getElementsByTagName('ul')[0];
				var li = arr[i].getElementsByTagName('li')[0];
				var a = arr[i].getElementsByTagName('a')[0];

				var pair = new Array(a,ul);
				pairs.push(pair);
			}
		}
	}
	return pairs;
};

var bindToLinks = function(arr)
{
	for (var n in arr)
	{
		shrink_ul(arr[n][1]);
		arr[n][0].onclick = scopepreserver(n,arr);
	}
};
	
function bindLeftNav() {
	var navigation = document.getElementById('leftnav');
	var pairs = getPairedArray(navigation);
	bindToLinks(pairs);
}