At maturity, the call option holder will "exercise", i.e. choose stock, with value
S, if the
stock price is above the strike
K to the option issuer,
S-K. The put option holder will exercise, receiving
K while surrendering
S, if the stock price is below
Therefore the value at maturity is equal to
Return a version of v at time t corrected for any optionality conditions.
recovery_fcn(v, S, t, ...)
Return recovery value, given non-default values v at time t. Subclasses may be more elaborate, this method simply returns 0.0.