There’s a Scala User Group in Gothenburg that had several meetings during this summer.  In one of the meetings the group solved a Kata named KataRomanNumerals (A Kata is a small problem that you do over and over again to learn)

The KataRomanNumerals says you should write a function to convert from normal numbers to Roman Numerals: e.g.

1 –> I

10 –> X

7 –> VII

Unfortunately I could not attend at this meeting, so I had to do it on my own during a few summer nights when my family finally was asleep :-).

Here’s my solution:

object Program extends Application {

class RomanInt(number: Int) {

def toRomanString() = {

val ones = List(“”, “I”, “II”, “III”, “IV”, “V”, “VI”, “VII”, “VIII”, “IX”);

val tens = List(“”, “X”, “XX”, “XXX”, “XL”, “L”, “LX”, “LXX”, “LXXX”, “XC”);

val hundreds = List(“”, “C”, “CC”, “CCC”, “CD”, “D”, “DC”, “DCC”, “DCCC”, “CM”);

val thousands = List(“”, “M”, “MM”, “MMM”);

thousands(part(1000)) + hundreds(part(100)) + tens(part(10)) + ones(part(1))

}

def part(digit: Int) = {

number % (digit * 10) / digit

}

}

implicit def Int2RomanInt(number: Int) = new RomanInt(number)

println(154.toRomanString()) // prints ‘CLVIII’

}

Here’s the code with better formatting.

Please comment and correct if I didn’t write idomatic Scala or if you have suggestions for improvements.

/Hans