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Updated the compound interest script

This commit is contained in:
Mike Cifelli 2017-03-04 16:33:05 -05:00
parent 946af24514
commit c20bb682f2
2 changed files with 12 additions and 10 deletions
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5
lisp/compound-interest-test.lisp
View File

@ -44,6 +44,9 @@
(assert= 81450 (compound-interest 100000 -5 4))
)
)
(defun negative-number-of-years ()
(assert= 100000 (compound-interest 100000 5 -4))
)
)
)

17
lisp/compound-interest.lisp
View File

@ -1,20 +1,19 @@
(defun decrement (n) (- n 1))
(defun percent (n percent)
(if (> percent 0)
(/ (+ (* n percent) 50) 100)
(/ (- (* n percent) 50) 100)
(defun percent (n percentage)
(if (> percentage 0)
(/ (+ (* n percentage) 50) 100)
(/ (- (* n percentage) 50) 100)
)
)
(defun compound-interest (principal rate years)
(if (= years 0)
(defun compound-interest (principal interest-rate years)
(if (< years 1)
principal
(compound-interest
(+ principal (percent principal rate))
rate
(+ principal (percent principal interest-rate))
interest-rate
(decrement years)
)
)
)