function LENGTH_MEASURES() {
	this.mKilometer = 1000;
	this.mMeter = 1;
	this.mDecimeter = 0.1;
	this.mCentimeter = 0.01;
	this.mMillimeter = 0.001;
	this.mMicronmeter = 0.000001;
	this.mLimeter = 500;
	this.mZhangmeter = 10 / 3;
	this.mChimeter = 1 / 3;
	this.mCunmeter = 1 / 30;
	this.mFenmeter = 1 / 300;
	this.mmLimeter = 1 / 3000;
	this.engFoot = 0.3048;
	this.engMile = 5280 * this.engFoot;
	this.engFurlong = 660 * this.engFoot;
	this.engYard = 3 * this.engFoot;
	this.engInch = this.engFoot / 12;
	this.nautMile = 1852;
	this.nautFathom = 6 * this.engFoot;
}
var length_data = new LENGTH_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,length_data);
}