function POWER_MEASURES() {
	this.Watt = 0.001
	this.Kilowatt = 1
	this.Horsepower = 0.745712172
	this.mHorsepower = 0.7352941
	this.kgms = 0.0098039215
	this.kcals = 4.1841004
	this.Btus = 1.05507491
	this.ftlbs = 0.0013557483731
	this.Js = 0.001
	this.Nms = 0.001
}
var power_data = new POWER_MEASURES();
function checkNum(str) {
	for (var i=0; i<str.length; i++)
	{
		var ch = str.substring(i, i + 1)
		if (ch!="." && ch!="+" && ch!="-" && ch!="e" && ch!="E" && (ch < "0" || ch > "9"))
		{
			alert("请输入有效的数字");
			return false;
		}
	}
	return true
}
function normalize(what,digits) {
	var str=""+what;
	var pp=Math.max(str.lastIndexOf("+"),str.lastIndexOf("-"));
	var idot=str.indexOf(".");
	if (idot>=1)
	{
		var ee=(pp>0)?str.substring(pp-1,str.length):"";
		digits+=idot;
		if (digits>=str.length)
			return str;
		if (pp>0 && digits>=pp)
			digits-=pp;
		var c=eval(str.charAt(digits));
		var ipos=digits-1;
		if (c>=5)
		{
			while (str.charAt(ipos)=="9")
				ipos--;
			if (str.charAt(ipos)==".")
			{
				var nc=eval(str.substring(0,idot))+1;
				if (nc==10 && ee.length>0)
				{
					nc=1;
					ee="e"+(eval(ee.substring(1,ee.length))+1);
				}
				return ""+nc+ee;
			}
			return str.substring(0,ipos)+(eval(str.charAt(ipos))+1)+ee;
		}
		else
			var ret=str.substring(0,digits)+ee;
		for (var i=0; i<ret.length; i++)
				if (ret.charAt(i)>"0" && ret.charAt(i)<="9")
					return ret;
		return str;
	}
	return str;
}
function compute(obj,val,data) {
	if (obj[val].value)
	{
		var uval=0;
		uval = obj[val].value*data[val];
		if( (uval >= 0) && (obj[val].value.indexOf("-") != -1) )
		{
			uval = -uval;    
		}
		for (var i in data)
			obj[i].value=normalize(uval/data[i],8);
	}
}
function resetValues(form,data)  {  
		for (var i in data)
			form[i].value="";
}
function resetAll(form) {   
	resetValues(form,power_data); 
}