58 lines
1.5 KiB
Common Lisp
58 lines
1.5 KiB
Common Lisp
(load "../lang/dlambda.lisp")
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(let ((static))
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(setq static
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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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(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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(years-passed 0))
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(setq private
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(eval
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(dlambda
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(:add-years (years)
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(if (> years 0)
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(setq years-passed (+ years-passed years))))
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(:compound-interest (years)
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(if (> years 0)
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(begin
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(setq principal
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(+ principal
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(call static :percent-of-number principal interest-rate)))
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(call private :compound-interest (- years 1))))))))
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(setq public
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(eval
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(dlambda
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(:get-years-passed ()
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years-passed)
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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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(:set-interest-rate (new-interest-rate)
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(setq interest-rate new-interest-rate))
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(:make-contribution (contribution)
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(setq principal (+ principal contribution)))
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(:move-forward-years (years)
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(call private :compound-interest years)
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(call private :add-years years))))))))
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