// recursive function to calculate interest
public double RecursiveCalc(DateTime cutOffDate, double rate, Transaction[] transactions,
double balance, double acquiredInterest)
{
if (!transactions.Any()) return 0;
Transaction trx = transactions[0];
if (transactions.Length == 1)
{
int days = (cutOffDate - trx.Date).Days;
acquiredInterest += (trx.Amount+balance).DailyInterest(rate, days);
return acquiredInterest;
}
else
{
int days = (transactions[1].Date - transactions[0].Date).Days;
balance += transactions[0].Amount;
acquiredInterest=acquiredInterest + (balance.DailyInterest(rate, days));
return RecursiveCalc(cutOffDate, rate, transactions.Skip(1).ToArray(), balance, acquiredInterest);
}
}