From: Gennady Bystritsky <Gennady.Bystritsky@...>
Date: 2009-11-11T10:23:02+09:00
Subject: Re: Roman Numerals (Arrgh!)

Well, considering that you at least started thinking on the problem and did some research, I am going to give you a solution. With a twist, of course -- it uses "advanced" array's method inject() that I wouldn't dare showing to your professors without being able to explain it. So work through it and simplify for your homework:

NOTE: The following code does not take into account the "subtraction rule".

$numerals = [[1000, "M"], [500, "D"], [100, "C"], [50, "L"], [10, "X"], [5, "V"], [1, "I"]]

def roman_numeral(number)
 $numerals.inject(["", number]) { |result, numeral|
   [ result[0] + numeral[1] * (result[1] / numeral[0]), number % numeral[0] ]
 }.first
end

p roman_numeral(1)   # => "I"
p roman_numeral(4)   # => "IIII"
p roman_numeral(5)   # => "V"
p roman_numeral(6)   # => "VI"
p roman_numeral(10)  # => "X"
p roman_numeral(19)  # => "XVIIII"
p roman_numeral(21)  # => "XXI"
p roman_numeral(180) # => "CLXXX"
p roman_numeral(949) # => "DCCCCXXXXVIIII"

On Nov 10, 2009, at 3:56 PM, Rick Barrett wrote:

> I have a homework assignment where I have to convert an inputted integer
> into Roman Numerals. I was doing fine building upon the previous steps
> until the arrays came in. We have to use the format/guidelines the
> professors give us or we get points counted off. I've looked at so many
> ways to do this program through Google, but none of the examples I've
> seen are even close to what the professor wrote out.
> 
> Basically, in my code I have to use the array $numerals and create pairs
> with the integer and its corresponding Roman Numeral.
> 
> What I can't figure out how to do is say something like...
> 
> For each 10 of the inputted number put an X
> 
> I was thinking something along the lines of dividing the inputted number
> by the decimal and taking the remaining integer and multiplying the
> Roman Numeral by that integer.
> 
> Like 30/10 = 3 so "X" * 3 would print out XXX
> 
> But I have no idea how to do that with the $numerals array.
> 
> How do I get my program to say divide the inputted number by the decimal
> part of the pair and then give the numeral part that many times?
> 
> def roman_numeral(number)
> 
> $numerals = [[10, "X"],
>      [5, "V"],
>      [1, "I"]]
> 
> result = ""
> 
>  $numerals.each() do |decimal, numeral|
> 
> 
>  result = new_variable
>  end
> 
>  return result
> end
> 
> puts "Enter a number to be converted to Roman Numerals."
> my_number = gets().chomp().to_i()
> puts roman_numeral(my_number)
> -- 
> Posted via http://www.ruby-forum.com/.
> 


Sincerely,
Gennady Bystritsky

Software Developer 4
Quest Software, Inc.
Aliso Viejo, CA