commit4e626ce82569870ec779fbd4f6dfc75b45994e1aparent782b624edd671b2c913418b17bd365573d04017aAuthor:dwrz <dwrz@dwrz.net>Date:Fri, 8 Feb 2019 00:24:07 +0000 Add elisp/roman-numeralsDiffstat:

A | elisp/roman-numerals/README.md | | | 49 | +++++++++++++++++++++++++++++++++++++++++++++++++ |

A | elisp/roman-numerals/roman-numerals-test.el | | | 30 | ++++++++++++++++++++++++++++++ |

A | elisp/roman-numerals/roman-numerals.el | | | 46 | ++++++++++++++++++++++++++++++++++++++++++++++ |

3 files changed, 125 insertions(+), 0 deletions(-)diff --git a/elisp/roman-numerals/README.md b/elisp/roman-numerals/README.md@@ -0,0 +1,49 @@ +# Roman Numerals + +Write a function to convert from normal numbers to Roman Numerals. + +The Romans were a clever bunch. They conquered most of Europe and ruled +it for hundreds of years. They invented concrete and straight roads and +even bikinis. One thing they never discovered though was the number +zero. This made writing and dating extensive histories of their exploits +slightly more challenging, but the system of numbers they came up with +is still in use today. For example the BBC uses Roman numerals to date +their programmes. + +The Romans wrote numbers using letters - I, V, X, L, C, D, M. (notice +these letters have lots of straight lines and are hence easy to hack +into stone tablets). + +``` + 1 => I +10 => X + 7 => VII +``` + +There is no need to be able to convert numbers larger than about 3000. +(The Romans themselves didn't tend to go any higher) + +Wikipedia says: Modern Roman numerals ... are written by expressing each +digit separately starting with the left most digit and skipping any +digit with a value of zero. + +To see this in practice, consider the example of 1990. + +In Roman numerals 1990 is MCMXC: + +1000=M +900=CM +90=XC + +2008 is written as MMVIII: + +2000=MM +8=VIII + +See also: http://www.novaroma.org/via_romana/numbers.html +## Source + +The Roman Numeral Kata [http://codingdojo.org/cgi-bin/index.pl?KataRomanNumerals](http://codingdojo.org/cgi-bin/index.pl?KataRomanNumerals) + +## Submitting Incomplete Solutions +It's possible to submit an incomplete solution so you can see how others have completed the exercise.diff --git a/elisp/roman-numerals/roman-numerals-test.el b/elisp/roman-numerals/roman-numerals-test.el@@ -0,0 +1,30 @@ +;;; roman-numerals-test.el --- Tests for roman-numerals (exercism) + +;;; Commentary: + +;;; Code: + +(load-file "roman-numerals.el") + +(ert-deftest roman-numerals-test () + (should (equal (to-roman 1) "I")) + (should (equal (to-roman 2) "II")) + (should (equal (to-roman 3) "III")) + (should (equal (to-roman 4) "IV")) + (should (equal (to-roman 5) "V")) + (should (equal (to-roman 6) "VI")) + (should (equal (to-roman 9) "IX")) + (should (equal (to-roman 27) "XXVII")) + (should (equal (to-roman 48) "XLVIII")) + (should (equal (to-roman 59) "LIX")) + (should (equal (to-roman 93) "XCIII")) + (should (equal (to-roman 141) "CXLI")) + (should (equal (to-roman 163) "CLXIII")) + (should (equal (to-roman 402) "CDII")) + (should (equal (to-roman 575) "DLXXV")) + (should (equal (to-roman 911) "CMXI")) + (should (equal (to-roman 1024) "MXXIV")) + (should (equal (to-roman 3000) "MMM"))) + +(provide 'roman-numerals) +;;; roman-numerals-test.el ends herediff --git a/elisp/roman-numerals/roman-numerals.el b/elisp/roman-numerals/roman-numerals.el@@ -0,0 +1,46 @@ +;;; roman-numerals.el --- roman-numerals Exercise (exercism) + +;;; Commentary: + +;;; Code: + +(provide 'roman-numerals) + +(defun greatest-roman-amount (n) + (cond ((>= n 1000) 1000) + ((>= n 900) 900) + ((>= n 500) 500) + ((>= n 400) 400) + ((>= n 100) 100) + ((>= n 90) 90) + ((>= n 50) 50) + ((>= n 40) 40) + ((>= n 10) 10) + ((>= n 9) 9) + ((>= n 5) 5) + ((>= n 4) 4) + ((>= n 1) 1))) + +(defun numeral-for-amount (n) + (cond ((= n 1000) "M") + ((= n 900) "CM") + ((= n 500) "D") + ((= n 400) "CD") + ((= n 100) "C") + ((= n 90) "XC") + ((= n 50) "L") + ((= n 40) "XL") + ((= n 10) "X") + ((= n 9) "IX") + ((= n 5) "V") + ((= n 4) "IV") + ((= n 1) "I"))) + +(defun to-roman (n) +"Convert whole number N to roman numeral. +Does not handle numbers greater than 3000." + (cl-loop until (<= n 0) + concat (numeral-for-amount (greatest-roman-amount n)) + do (setq n (- n (greatest-roman-amount n))))) + +;;; roman-numerals.el ends here