From: Raf Coremans <rrafje@...>
Date: 2007-05-10T06:38:12+09:00
Subject: Re: What's the most ruby-ish way to write this python code?

2007/5/9, Drew Olson <olsonas@gmail.com>:
> All -
>
> I've been using ruby for quite some time and I'm only beginning to look
> at python. I really like the way ruby flows as compared to python and I
> can't see myself getting pulled away from ruby. However, there is one
> thing I like about python, and that is the generators. What is the best
> way to translate the following code into ruby? Assume word is some
> string and letters is a string of all the characters a..z:
>
> [word[0:i]+c+word[i+1:] for i in range(len(word)) for c in letters]
>
> This is all based on trying to efficiently rewrite
> http://norvig.com/spell-correct.html in ruby. Essentially what this code
> does is get the array of words resulting from inserting every character
> at every possible position in the given word. I find it pretty succinct,
> but I know ruby can do better! I've come up with two ways to do this in
> ruby, but neither seems to "click" with me:
>
> (0...word.size).inject([]) do |words,i|
>   letters.split('').each do |c|
>     words << word[0...i]+c+word[i..-1]
>   end
>   words
> end
>
> OR
>
> (0...words.size).map do |i|
>   letters.split('').map do |c|
>     word[0...i]+c+word[i..-1]
>   end
> end.flatten
>
> Any advice? Currenty, I'm using the first approach and it's sloooooow
> (I'm assuming inject has high overhead).
>
> --
> Posted via http://www.ruby-forum.com/.
>
>

Both ways seem ruby-esque to me.

Note though that you should use word[i+1..-1] (not word[i..-1]) in
order to get the same result as your python code.

The fastest executing algorithm that I could find was:
ar = []
(0...word.size).each do |i|
  letters.split(//).each do |c|
    ar << word.dup
    ar[-1][i] = c
  end
end

Regards,
Raf