/**
 * XIRR is used to determine the Internal Rate of Return when the cash flows are at Irregular intervals.
 *
 * @see http://www.financialwisdomforum.org/gummy-stuff/xirr.htm
 * @param cfs
 * @param dts
 * @param guess
 * @returns
 */
export declare function XIRR(cfs: number[], dts: Date[], guess?: number): number | null;