diff options
| -rw-r--r-- | src/economy.cpp | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/src/economy.cpp b/src/economy.cpp index a6fbb55f2..3c220d329 100644 --- a/src/economy.cpp +++ b/src/economy.cpp @@ -639,12 +639,23 @@ static void AddInflation(bool check_year = true) static void CompaniesPayInterest() { const Company *c; - int interest = _economy.interest_rate * 54; FOR_ALL_COMPANIES(c) { _current_company = c->index; - SubtractMoneyFromCompany(CommandCost(EXPENSES_LOAN_INT, (Money)BigMulSU(c->current_loan, interest, 16))); + /* Over a year the paid interest should be "loan * interest percentage", + * but... as that number is likely not dividable by 12 (pay each month), + * one needs to account for that in the monthly fee calculations. + * To easily calculate what one should pay "this" month, you calculate + * what (total) should have been paid up to this month and you substract + * whatever has been paid in the previous months. This will mean one month + * it'll be a bit more and the other it'll be a bit less than the average + * monthly fee, but on average it will be exact. */ + Money yearly_fee = c->current_loan * _economy.interest_rate / 100; + Money up_to_previous_month = yearly_fee * _cur_month / 12; + Money up_to_this_month = yearly_fee * (_cur_month + 1) / 12; + + SubtractMoneyFromCompany(CommandCost(EXPENSES_LOAN_INT, up_to_this_month - up_to_previous_month)); SubtractMoneyFromCompany(CommandCost(EXPENSES_OTHER, _price.station_value >> 2)); } |