Roman numerals

We use this kata to develop the concepts of Transformation Priority Premise

Overview

Roman numerals is a numbering system which uses Latin alpha characters to represent a known set of numbers and combinations of these to represent all others.

Objectives

Write a function which can take any integer from 1-1000 and return its Roman numeral representation as a string.

• Combine Roman numerals to make bigger numbers, e.g. I = 1, II = 2 (1 + 1), VI = 6 (5 + 1). Larger numerals come before (left of) smaller ones.

• You cannot combine more than three of the same numeral, e.g. IIII = 4 is not valid. Instead, you must use the next numeral up and prefix it with a numeral to subtract from it, e.g. IV = 4 (1 less than 5), XL = 40 (10 less than 50). You can spot these exceptional cases because the smaller numeral comes before (left of) the larger.

Further information on Roman numerals can be found here: http://mathworld.wolfram.com/RomanNumerals.html

Examples

Single character numerals

Arabic number	Roman numeral	Arabic number	Roman numeral
1	I	5	V
10	X	50	L
100	C	500	D
1000	M

Basic conversions

Arabic number	Roman numeral	Arabic number	Roman numeral	Arabic number	Roman numeral
2	II	20	XX	200	CC
3	III	30	XXX	300	CCC
4	IV	40	XL	400	CD
6	VI	60	LX	600	DC
7	VII	70	LXX	700	DCC
8	VIII	80	LXXX	800	DCCC
9	IX	90	XC	900	CM

More advanced conversions

Arabic number	Roman numeral	Hundreds	Tens	Units
42	XLII	-	XL	II
584	DLXXXIV	D	LXXX	IV
777	DCCLXXVIII	DCC	LXX	VII
999	CMXCIX	CM	XC	IX