#!/usr/bin/env ruby -w
#
# "Modern" Roman numerals
# "Learn to Program" by Chris Pine, p. 76


def roman_numeral n
	result = ''

	result << 'M' * (n / 1000)
	n = n % 1000
	if n >= 900
		result << 'CM'
		n = n - 900
	end

	result << 'D' * (n / 500)
	n = n % 500
	if n >= 400
		result << 'CD'
		n = n - 400
	end

	result << 'C' * (n / 100)
	n = n % 100
	if n >= 90
		result << 'XC'
		n = n - 90
	end

	result << 'L' * (n / 50)
	n = n % 50
	if n >= 40
		result << 'XL'
		n = n - 40
	end
	
	result << 'X' * (n / 10)
	n = n % 10
	if n >= 9
		result << 'IX'
		n = n - 9
	end

	result << 'V' * (n / 5)
	n = n % 5
	if n >= 4
		result << 'IV'
		n = n - 4
	end

	result << 'I' * n
end

test_values = [
	['I',       1],
	['II',      2],
	['III',     3],
	['IV',      4],
	['V',       5],
	['VI',      6],
	['VII',     7],
	['VIII',    8],
	['IX',      9],
	['X',       10],
	['XI',      11],
	['XII',     12],
	['XIII',    13],
	['XIV',     14],
	['XV',      15],
	['XVI',     16],
	['XVII',    17],
	['XVIII',   18],
	['XIX',     19],
	['XX',      20],
	['XXX',     30],
	['XL',      40],
	['L',       50],
	['LX',      60],
	['LXX',     70],
	['LXXX',    80],
	['XC',      90],
	['XCIX',    99],
	['C',       100],
	['CC',      200],
	['CD',      400],
	['D',       500],
	['CM',      900],
	['M',       1000],
	['MIX',     1009],
	['MCMXLV',  1945],
	['MCMXCIX', 1999],
	['MM',      2000],
	['MMM',     3000],
]

success = true
test_values.each do |roman, arabic|
	test = roman_numeral arabic
	if test == roman
		puts "PASS: #{arabic} is #{test}"
	else
		puts "ERROR: #{arabic} is #{test}, should be #{roman}"
		success = false
	end
end

exit unless success

n = 0
while n <= 3000
	puts "#{n}: " + roman_numeral(n)
	n = n + 1
end