47 lines
1.1 KiB
EmacsLisp
47 lines
1.1 KiB
EmacsLisp
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;;; roman-numerals.el --- roman-numerals Exercise (exercism)
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;;; Commentary:
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;;; Code:
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(provide 'roman-numerals)
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(defun greatest-roman-amount (n)
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(cond ((>= n 1000) 1000)
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((>= n 900) 900)
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((>= n 500) 500)
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((>= n 400) 400)
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((>= n 100) 100)
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((>= n 90) 90)
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((>= n 50) 50)
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((>= n 40) 40)
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((>= n 10) 10)
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((>= n 9) 9)
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((>= n 5) 5)
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((>= n 4) 4)
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((>= n 1) 1)))
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(defun numeral-for-amount (n)
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(cond ((= n 1000) "M")
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((= n 900) "CM")
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((= n 500) "D")
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((= n 400) "CD")
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((= n 100) "C")
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((= n 90) "XC")
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((= n 50) "L")
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((= n 40) "XL")
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((= n 10) "X")
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((= n 9) "IX")
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((= n 5) "V")
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((= n 4) "IV")
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((= n 1) "I")))
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(defun to-roman (n)
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"Convert whole number N to roman numeral.
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Does not handle numbers greater than 3000."
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(cl-loop until (<= n 0)
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concat (numeral-for-amount (greatest-roman-amount n))
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do (setq n (- n (greatest-roman-amount n)))))
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;;; roman-numerals.el ends here
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