From: Gennady Bystritsky <Gennady.Bystritsky@...>
Date: 2009-11-12T05:16:36+09:00
Subject: Re: Roman Numerals (Arrgh!)


On Nov 11, 2009, at 11:59 AM, Benoit Daloze wrote:

> Well, being student as well, I'd love to study Ruby instead of this (****)
> Java. (Where are you studying?) But that's not the point.
> 
> So, here is my piece of advice:
> 
> Using $numerals = [
>  [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"]
> ]
> 
> ,you should iterate on each of them, seeing how much your number have of
> this kind (/)
> and what is the rest after that, to use it for the next step(%)...
> (if you use Array#each, you'll get a new array(let's say a) like a=[dec,
> romanString]. You can then take them separetely by a[0] and a[1].
> Even if this method is not that beautiful in Ruby, it's the easiest way to
> understand how to do it).
> 
> That the way used in a very known book of Ruby.
> 
> You just need to manage how to save this in your String at each step.
> (You can multiply a String by "X" * 3, and concatenate using << (or +=))
> 
> Give us your script when you'll got one working ;)

In case you have missed it from yesterday, a slightly modified original solution was:

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

It works with shortened numerals for 4, 9, 40, 90, 400, 900 as well.

Gennady.