logenkain/mortgage-calculator
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Refactor monthly totals

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Logen Kain 2020-10-28 17:01:09 -04:00
parent 4280ae7585
commit 967d7d594d
1 changed files with 9 additions and 8 deletions
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17
mortgage-calculator.lisp
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@ -23,28 +23,29 @@ P * (1-(1+r)^-n) = r * PV
|#
(defun find-payments (loan-total rate number-of-payments)
"Base loan calculation"
"Generic payment calculation"
(/ (* rate loan-total)
(- 1 (expt (+ 1 rate) (* number-of-payments -1)))))
(defun find-monthly-payments(loan-total rate number-of-payments)
"Modify loan calculation to show monthly payments"
"Monthly payment by loan/rate/number of years"
(find-payments loan-total (/ rate 12) (* number-of-payments 12)))
(defun find-montly-payment-total-per-year (loan-total rate number-of-payments)
"Modify loan calculation to show total montly payments per year"
(* (find-payments loan-total (/ rate 12) (* number-of-payments 12)) 12))
(defun find-monthly-payment-total-per-year (loan-total rate number-of-payments)
"Total monthly payments per year"
(* (find-monthly-payments loan-total rate number-of-payments) 12))
;; fixme: add function to take monthly-payments rate num-of-payments
(defun find-biggest-loan (payments rate number-of-payments)
"Base loan calculation"
"Generic loan calculation"
(/ (* payments
(- 1 (expt (+ 1 rate)
(* -1 number-of-payments))))
(- 1
(expt (+ 1 rate) (* -1 number-of-payments))))
rate))
(defun find-biggest-loan-monthly (payments rate number-of-payments)
"Largest loan by payments/interest rate/number of years"
(find-biggest-loan payments (/ rate 12) (* number-of-payments 12)))