From: Gennady Bystritsky <Gennady.Bystritsky@...>
Date: 2009-11-11T12:30:48+09:00
Subject: Re: Roman Numerals (Arrgh!)


On Nov 10, 2009, at 6:43 PM, Rob Biedenharn wrote:

> On Nov 10, 2009, at 8:49 PM, Gennady Bystritsky wrote:
> 
>> On Nov 10, 2009, at 5:37 PM, Rob Biedenharn wrote:
>> 
>>> On Nov 10, 2009, at 6:56 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
>>>> 
>>> 
>>> P.S. I saw Gennady's post, but I'd argue that no one would really  
>>> want
>>> to solve the problem that way. And Nik's way doesn't give any help
>> 
>> Why not that way? It works and it is short ;-)
>> 
>> Gennady.
> 
> Not that it doesn't work, just that it might be easier/quicker to  
> rewrite than to understand. Short isn't *always* a virtue and if  
> there's a reason (performance?) to be terse, then there ought to be a  
> comment by way of explanation.
> 
> There are few truly necessary uses of Enumerable#inject and this isn't  

I respectfully disagree. inject() is a very powerful facility that allows quick elegant implementation of many tasks at hand. I usually start with an inject()-based implementation (where appropriate) and then may refactor it later if performance is not satisfactory. The latter does not happen very often, though. As for the virtue, the less code you write the fewer bugs get in -- especially when you use well tested standard facilities like inject().

> one of them, but if it were, I'd make it at least slightly more  
> readable:
> 
>   def roman_numeral(number)
>     $numerals.inject(["", number]) { |(answer, number), (arabic,  
> roman)|

For that thanks a lot -- somehow I missed the fact it is possible in ruby.

>       [ answer + roman * (number / arabic), number % arabic ]
>     }.first
>   end
> 
> And with an appropriately formed $numerals array, the "subtraction  
> rule" is already covered. ;-)

Would you please elaborate? You mean same algorithm and "better" $numerals would cover mapping of 4 => "IV", 9 => "IX", etc.?

> 
> -Rob
> 
> Rob Biedenharn		http://agileconsultingllc.com
> Rob@AgileConsultingLLC.com
> 
> 
> 
>