* COUPDAYBS
*
* Returns the number of days from the beginning of the coupon period to the settlement date.
*
* Excel Function:
* COUPDAYBS(settlement,maturity,frequency[,basis])
*
* @access public
* @category Financial Functions
*
* COUPDAYS
*
* Returns the number of days in the coupon period that contains the settlement date.
*
* Excel Function:
* COUPDAYS(settlement,maturity,frequency[,basis])
*
* @access public
* @category Financial Functions
*
* COUPDAYSNC
*
* Returns the number of days from the settlement date to the next coupon date.
*
* Excel Function:
* COUPDAYSNC(settlement,maturity,frequency[,basis])
*
* @access public
* @category Financial Functions
*