Roman Numerals Kata

roman_numerals.rb

# Feb, 27th, 2012
# Kevin and Jared at Mad Railers
# run with rspec

require 'rubygems'
require 'rspec'

def roman(number)
  output = ""
  conversion_table = { 1000 => "M", 900 => "CM", 500 => "D", 400 => "CD", 100 => "C", 90 => "XC", 50 => "L", 40 => "XL", 10 => "X", 9 => "IX", 5 => "V", 4 => "IV", 1 => "I" }

  leftover = number

  conversion_table.each do |arabic, numeral|
    quotient  = leftover / arabic
    remainder = leftover % arabic
    if quotient > 0
      output << numeral * quotient
    end
    leftover = remainder
  end
  output
end

describe 'roman numerals' do
  it "returns 1" do
    roman(1).should == "I"
  end

  it "returns 2" do
    roman(2).should == "II"
  end

  it "returns 3" do
    roman(3).should == "III"
  end

  it "returns 4" do
    roman(4).should == "IV"
  end

  it "returns 5" do
    roman(5).should == "V"
  end

  it "returns 6" do
    roman(6).should == "VI"
  end

  it "returns 7" do
    roman(7).should == "VII"
  end

  it "returns 9" do
    roman(9).should == "IX"
  end

  it "returns 10" do
    roman(10).should == "X"
  end

  it "returns 11" do
    roman(11).should == "XI"
  end

  it "returns 14" do
    roman(14).should == "XIV"
  end

  it "returns 17" do
    roman(17).should == "XVII"
  end

  it "returns 37" do
    roman(37).should == "XXXVII"
  end

  it "returns 40" do
    roman(40).should == "XL"
  end

  it "returns 42" do
    roman(42).should == "XLII"
  end

  it "returns 51" do
    roman(51).should == "LI"
  end

  it "returns 100" do
    roman(100).should == "C"
  end

  it "returns 101" do
    roman(101).should == "CI"
  end

  it "returns 556" do
    roman(556).should == "DLVI"
  end

  it "returns 1205" do
    roman(1205).should == "MCCV"
  end

  it "returns 88" do
    roman(88).should == "LXXXVIII"
  end

  it "returns 999" do
    roman(999).should == "CMXCIX"
  end
end