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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)) (assert= 81450 (compound-interest 100000 -5 4))
) )
(defun negative-number-of-years ()
(assert= 100000 (compound-interest 100000 5 -4))
)
) )
) )

17
lisp/compound-interest.lisp
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@ -1,20 +1,19 @@
(defun decrement (n) (- n 1)) (defun decrement (n) (- n 1))
(defun percent (n percent) (defun percent (n percentage)
(if (> percent 0) (if (> percentage 0)
(/ (+ (* n percent) 50) 100) (/ (+ (* n percentage) 50) 100)
(/ (- (* n percent) 50) 100) (/ (- (* n percentage) 50) 100)
) )
) )
(defun compound-interest (principal rate years) (defun compound-interest (principal interest-rate years)
(if (= years 0) (if (< years 1)
principal principal
(compound-interest (compound-interest
(+ principal (percent principal rate)) (+ principal (percent principal interest-rate))
rate interest-rate
(decrement years) (decrement years)
) )
) )
) )