var preferredUnitElements = new Array();
var altUnitElements = new Array();
var measureSelectors = new Array();
var measureSystems = new Object();
var userSelectedMeasureSystem = '';

function showUnits( selector )
{
	var what = selector.options[selector.selectedIndex].value;

	if( what == "preferred" ) {
		showPreferredElements();
	}
	else {
		showAltElements();
	}
	
	for( var i=0; i<measureSelectors.length; ++i ) {
		var elem = document.getElementById( measureSelectors[i] );
		if( elem == null )
			continue;
		for( var j=0; j<elem.options.length; ++j ) {
			if( elem.options[j].value == what ) {
				elem.options[j].selected = true;
				userSelectedMeasureSystem = measureSystems[what];
			}
		}
	}
}

function showPreferredElements()
{
	for( var i=0; i<preferredUnitElements.length; ++i ) {
		var elem = document.getElementById( preferredUnitElements[i] );
		if( elem != null ) {
			elem.style.display = "inline";
		}
	}
	
	for( var i=0; i<altUnitElements.length; ++i ) {
		var elem = document.getElementById( altUnitElements[i] );
		if( elem != null ) {
			elem.style.display = "none";
		}
	}
}

function showAltElements()
{
	for( var i=0; i<altUnitElements.length; ++i ) {
		var elem = document.getElementById( altUnitElements[i] );
		if( elem != null ) {
			elem.style.display = "inline";
		}
	}
	
	for( var i=0; i<preferredUnitElements.length; ++i ) {
		var elem = document.getElementById( preferredUnitElements[i] );
		if( elem != null ) {
			elem.style.display = "none";
		}
	}
}