From: Alphonse 23 <lists@...>
Date: 2013-06-01T05:04:07+09:00
Subject: Re: Eloquent Ruby Kaprekar's Number

Admin Tensor wrote in post #1110741:
> Hi,
>
> Yes, Kaprekar number is good to be an exercise in creating a (Ruby)
> code, but after googling it, what are the practical applications for
> Kaprekar numbers?
>

There isn't any, I believe. Though there could be a use for them in the
future. I used Kaprekar's number because it's simple. This was just an
exercise in writing ruby code, specifically how to write good readable
"eloquent" code.

Peter Hickman wrote in post #1110774:
> You never use ks as it is you always use ks.to_s so we might was well go
> with that and make is easier to read.
> The line breaks make it more obvious as to the steps you are taking.
>
> Again it is just a personal preference.
>
> Finally the simple_test code does not work for failures.

Woops, sorry about that. Yes, the simple_test code is really bad. I'm
still learning how to use Rspec.

After reviewing everyone else's algorithms here's my new version. I
believe this is the most readable and rubyist like.

def kaprekar?(num)
  return false if num.zero?

  num_square = (num**2).to_s
  num_len = num_square.length
  midpoint = (num_len / 2)-1

  left = num_square[0..midpoint].to_i
  right = num_square[midpoint+1..-1].to_i

  num == left + right
end

p kaprekar?(9)
p kaprekar?(297)

Now I need to go learn Rspec..

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