From: Rick DeNatale <rick.denatale@...>
Date: 2007-03-02T00:43:29+09:00
Subject: Re: Sorting a Hash

On 2/28/07, Nasir Khan <rubylearner@gmail.com> wrote:

> I want to order such that the keys (or values) when returned in an array are
> ordered.
> Obviously the above snipper does *not* work because Hash#sort does not sort
> the Hash but returns an array of arrays with elements sorted according to
> sort block.
>
> I can maintain a parallel array of sorted keys but it is kind of kludgy.
> Can I sort the hash "in place" such that the Hash#keys and Hash#values
> return sorted results, without me having to maintain this array of arrays
> separately?

Well there's nothing stopping you from adding methods to Hash to
return sorted keys and values.  Of course you can also just do

hash.keys.sort
or
hash.values.sort

The first one will likely do what you want, but I suspect that what
you really want for values is to get them as ordered by the sorted
keys.

Here's a quick implementation of two additional methods for hash, I
wouldn't recommend changing the implementation of the existing keys
and values methods:

rick@frodo:/public/rubyscripts$ cat shash.rb
class Hash

  def sorted_keys(&sort_block)
    keys.sort(&sort_block)
  end

  def values_sorted_by_keys(&sort_block)
    values_at(*sorted_keys(&sort_block))
  end
end

test_hash = {"Fred" => "Wilma", "Barney" => "Betty",
             "Ricky" => "Lucy", "Fred" => "Ethel",
             "Ralph" => "Alice", "Ed" => "Trixie"}

p test_hash.keys
p test_hash.values
p test_hash.sorted_keys
p test_hash.values_sorted_by_keys
p test_hash.sorted_keys {|a, b| b <=> a}
p test_hash.values_sorted_by_keys {|a, b| b <=> a}

rick@frodo:/public/rubyscripts$ ruby shash.rb
["Ralph", "Ricky", "Barney", "Fred", "Ed"]
["Alice", "Lucy", "Betty", "Ethel", "Trixie"]
["Barney", "Ed", "Fred", "Ralph", "Ricky"]
["Betty", "Trixie", "Ethel", "Alice", "Lucy"]
["Ricky", "Ralph", "Fred", "Ed", "Barney"]
["Lucy", "Alice", "Ethel", "Trixie", "Betty"]

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/