From: Ammar Ali <ammarabuali@...>
Date: 2010-11-07T19:48:18+09:00
Subject: Re: sort_by is not stable ?

On Sun, Nov 7, 2010 at 12:22 PM, Michel Demazure <michel@demazure.com> wrote:
> sort_by  is not a stable sorting method (ruby 1.9.2 p0)
>
> I am doing word statistics in a text file. I have a long array of
> entries [word, number], sorted by alphabetic order on word. When I sort
> on number, entries with the same number are shuffled.

Without code, I have to guess. If I understood your issue correctly,
then you need to specify both fields in sort_by block:

>> a = [["g", 3], ["c", 3], ["a", 3], ["f", 3], ["e", 2], ["d", 3], ["b", 1]]
=> [["g", 3], ["c", 3], ["a", 3], ["f", 3], ["e", 2], ["d", 3], ["b", 1]]
>> a.sort_by {|e| [e.last, e.first]}
=> [["b", 1], ["e", 2], ["a", 3], ["c", 3], ["d", 3], ["f", 3], ["g", 3]]

Regards,
Ammar