ch12_romanparty.rb

#Chapter 12.6 party like it's roman

def roman_to_integer roman
  digit_vals = {'i' =>    1,
                'v' =>    5, 
                'x' =>   10,
                'l' =>   50,
                'c' =>  100,
                'd' =>  500,
                'm' => 1000,}

total = 0
prev = 0
index = roman.length - 1
while index >= 0
  c = roman[index].downcase
  index = index - 1
  val = digit_vals[c]
  if !val
    puts 'This is not a valid roman numeral'
    return
  end

  if val < prev
    val = val * -1
  else
    prev = val
  end
  total = total + val
end
total
end

puts(roman_to_integer('mcmxcix'))
puts(roman_to_integer('CCCLXV'))