Made Code Dojo 1: Roman Numeral Kata

README.txt

FAILED

http://butunclebob.com/ArticleS.UncleBob.ThePrimeFactorsKata

Notes (cos I had to look up what Prime Factors were):
=====================================================

http://en.wikipedia.org/wiki/Prime_factor

Prime factors of a number are the prime numbers you would multiply together to get that original number as a result, e.g:
The prime factors of 18 are 2 and 3 (2 x 3 x 3 = 18).

Prime numbers are numbers that can only be evenly divided (no decimal points!) by 1 or themselves, eg:
3 can only be divided by 3 or 1, whereas 4 can be divided 1, 2 and 4.

UncleBob wrote the original kata in Ruby, and later Java, with tests the whole way.
The final algorithm was three lines of code (but 40 lines of test code).

roman_numeral.rb

class RomanNumerator
  attr_reader :value

  def initialize(value)
    @numerals = ['I','V','X','L','C','D','M']
    @value = value
  end

  def <(comparator)
    char_lt?(char, comparator.value[0])
  end

  private

    def char_lt?(numeral_1, numeral_2)
      @numerals.index(numeral_1) < @numerals.index(numeral_2)
    end
end

spec.rb

require 'rspec'
require_relative '../roman_numerator.rb'

describe "convert method" do

  before :each do
    @converter = RomanNumeralsConverter.new
  end

  it "returns 'XXII' from 'XX' plus 'II'" do
    ('XX' + 'II').should eq "XXII"
  end

end

describe "lesser number can be used to prefix a larger number" do

  it "IV is less than V" do
    iv = RomanNumerator.new("IV")
    v = RomanNumerator.new("V")
    (iv < v).should be_true
  end

  it "CM is less than M" do
    cm = RomanNumerator.new("CM")
    m = RomanNumerator.new("M")
    (cm < m).should be_true
  end

  it "X should be less than IC" do
    x = RomanNumerator.new("X")
    ic = RomanNumerator.new("IC")
    (x < ic).should be_true
  end

end

# Key:
#
# I == 1
# V == 5
# X == 10
# L == 50
# C == 100
# D == 500
# M == 1000

# Symbols are converted to numbers by adding together the values they represent

# A run of symbols shouldn't feature the same symbol more than three times in succession:
## i.e. III (3) is cool, IIII (4) is not cool

# To achieve the numbers the above restriction prevents us from getting,
# you can place a smaller value symbol before a larger value symbol,
# which indicates that the smaller value should be subtracted
## i.e. IV == 4, MCM == 1900 (M = 1000, CM == (1000 - 100)), XL == 40


# It looks like we can just throw the "no more than three identical symbols in a row" rule
# out the window when we get to 4000 for this dojo, as the concept of a "bar" is introduced at that point,
# which is a horizontal line (so, a bar) drawn above a symbol or symbols to indicate that those symbols
# should be multiplied by a 1000 (i.e. IV with a bar above it would 4000),
# and I don't know if those symbols can be represented in Ruby.
# Maybe we just create our own way of representing a bar?