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Roman Numerals

About this Kata

I wasn’t there, but I believe this Kata was performed at XP2001 by Kent Beck. Here is [a video of Karl Scotland doing this Kata in Excel at agile 2008] Here is [a video of JonJagger doing this Kata in Ruby using CyberDojo]

Difficulty - Easy.

Problem Description

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 [1]. 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)

Part I

The Kata says you should write a function to convert from normal numbers to Roman Numerals: eg

     1 --> I
     10 --> X
     7 --> VII


For a full description of how it works, take a look at [this useful reference website] : which includes an implementation of the Kata in javascript.

There is no need to be able to convert numbers larger than about 3000. (The Romans themselves didn’t tend to go any higher)

Part II

Write a function to convert in the other direction, ie numeral to digit


Comments from those who are working on this Kata

We tackled this Kata at this GothPy081007 meeting – EmilyBache

[Here’s a Scala solution], – HansBrattberg

Found a [F# solution] and a [tidy Ruby one] at github.

[Implementation] in ruby, java and clojure along with acceptance tests written in ruby and interacting with the command line. Would be nice with some additional languages. - FredrikRubensson

[Here’s a JavaScript solution] at Github