Is ExCoupon

Function Is ExCoupon within Bond with keys Bond Is ExCoupon keys returns true if the given settlement date Tˢ is on or after the ex coupon date of the accrual period(s) of the referenced bond(s) that includes(include) the date Tˢ
The financial interpretation is that if a purchased bond settles on Tˢ, the purchaser will skip (receive) the forthcoming coupon, if the function here returns true (false).

If the settlement date Tˢ is not explicitly given, it will be set to the bond's settlement date as implied by a trade transaction assumed to occur on the trade date T₀ (typically today).