function isval(x/*:?any*/)/*:boolean*/ { return x !== undefined && x !== null; }

function keys(o/*:any*/)/*:Array<any>*/ { return Object.keys(o); }

function evert_key(obj/*:any*/, key/*:string*/)/*:EvertType*/ {
	var o = ([]/*:any*/), K = keys(obj);
	for(var i = 0; i !== K.length; ++i) o[obj[K[i]][key]] = K[i];
	return o;
}

function evert(obj/*:any*/)/*:EvertType*/ {
	var o = ([]/*:any*/), K = keys(obj);
	for(var i = 0; i !== K.length; ++i) o[obj[K[i]]] = K[i];
	return o;
}

function evert_num(obj/*:any*/)/*:EvertNumType*/ {
	var o = ([]/*:any*/), K = keys(obj);
	for(var i = 0; i !== K.length; ++i) o[obj[K[i]]] = parseInt(K[i],10);
	return o;
}

function evert_arr(obj/*:any*/)/*:EvertArrType*/ {
	var o/*:EvertArrType*/ = ([]/*:any*/), K = keys(obj);
	for(var i = 0; i !== K.length; ++i) {
		if(o[obj[K[i]]] == null) o[obj[K[i]]] = [];
		o[obj[K[i]]].push(K[i]);
	}
	return o;
}

/* TODO: date1904 logic */
function datenum(v/*:number*/, date1904/*:?boolean*/)/*:number*/ {
	if(date1904) v+=1462;
	var epoch = Date.parse(v);
	return (epoch + 2209161600000) / (24 * 60 * 60 * 1000);
}

function cc2str(arr/*:Array<number>*/)/*:string*/ {
	var o = "";
	for(var i = 0; i != arr.length; ++i) o += String.fromCharCode(arr[i]);
	return o;
}