40 lines
1.1 KiB
Common Lisp
40 lines
1.1 KiB
Common Lisp
(load "../lang/dlambda.lisp")
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(defun interest-compounder (initial-principal initial-interest-rate)
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(let ((private) (public)
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(principal initial-principal)
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(interest-rate initial-interest-rate))
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(setf private
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(eval
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(dlambda
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(:percent-of-number (n percentage)
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(if (> percentage 0)
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(/ (+ (* n percentage) 50) 100)
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(/ (- (* n percentage) 50) 100)))
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(:compound-interest (years)
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(if (> years 0)
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(progn
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(setf principal
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(+ principal
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(call private :percent-of-number principal interest-rate)))
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(call private :compound-interest (- years 1))))))))
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(setf public
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(eval
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(dlambda
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(:get-principal ()
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principal)
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(:get-interest-rate ()
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interest-rate)
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(:move-forward-one-year ()
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(call private :compound-interest 1))
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(:move-forward-years (years)
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(call private :compound-interest years)))))))
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