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(svn r14825) -Fix: pay the correct amount of interest instead of a few percent too little a year

This commit is contained in:
rubidium 2009-01-04 14:32:30 +00:00
parent 8c33893ffd
commit 2283b8038f
1 changed files with 13 additions and 2 deletions
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15
src/economy.cpp
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@ -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));
}