Authors: Lisa, Snorre A quick and simple solution for converting from decimal numbers to roman numerals. It is based on a table (double array) lookup-algorithm using a digit's position in a number as well as its value to find the correct roman numeral to add to the roman numeral string/array.

gistfile1.rb

 class NumeralRomanConverter
    def initialize
        @romanTable = [ ["I","IV","V","IX"],
                        ["X","XL","L","LC"],
                        ["C","LC","D","CM"],
                        ["M"]]
    end
    
    def numeralToRoman(numeralValue)
        numberAsString = numeralValue.to_s
        numberAsString.reverse!
        romanNumeral = Array.new
        for i in 0..numberAsString.size
            value = numberAsString[i].to_i
            romanNumeral.unshift(getRomanNumeral(i+1,value))
        end
        romanNumeralString = ""
        for i in 0..romanNumeral.size-1
            romanNumeralString += romanNumeral[i]
        end
        puts numeralValue.to_s + " is " + romanNumeralString
    end
    
    def getRomanNumeral(digitNumber, value)
        digitPos = digitNumber-1
        romanNumerals = ""
        if value <= 3
            for i in 1..value
                romanNumerals += @romanTable[digitPos][0]
            end
            elsif value == 4
            romanNumerals += @romanTable[digitPos][1]
            elsif value == 5
            romanNumerals += @romanTable[digitPos][2]
            elsif value <= 8
            romanNumerals += @romanTable[digitPos][2]
            for i in 6..value
                romanNumerals += @romanTable[digitPos][0]
            end
            else
            romanNumerals += @romanTable[digitPos][3]
        end
        return romanNumerals
    end
end


converter = NumeralRomanConverter.new
converter.numeralToRoman(54)
converter.numeralToRoman(100)
converter.numeralToRoman(2999)
puts "Try your own numbers! (Type 'exit' to quit the program).."
input = ""
begin
    input = gets.chomp
    converter.numeralToRoman(input.to_i)
end while input != "exit"
puts "Good bye!"