From: "David A. Black" <dblack@...>
Date: 2009-06-19T22:09:16+09:00
Subject: Re: need a hash/iteration tutorial...text reading.

Hi --

On Fri, 19 Jun 2009, Matt Neuburg wrote:

> Steven Demonnin <tooltime@uncletoby.net> wrote:
>
>> What I want to know is, is it possible to create a has where the key is
>> the word, and the value is the number of occurrences of the word in the
>> text, and then sort the hash by the values?
>
> That is called a "histogram" and is one of the most common examples
> (Google is your friend). The sticking point here is what you mean by a
> "word". If you're willing to accept a fairly crude definition of this
> notion, then that is an example I develop in the Blocks section of my
> Ruby tutorial chapter here:
>
> http://www.apeth.com/ruby/02justenoughruby.html
>
> To sort, add this line:
>
> wds = h.sort {|x,y| x[1] <=> y[1]}

Or, slightly more compact:

   wds = h.sort_by {|x| x[1] }

> Note that the concept "sort a hash" has no real meaning, since a hash is
> not ordered. What you can do is to convert to an array and sort the
> array.

In 1.9 hashes are ordered, but by key-insertion order. You can't
change the order, so you can't sort back into a hash (unless you
create a new hash manually using the sorted order).


David

-- 
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