From: Robert Klemme <shortcutter@...>
Date: 2006-10-30T00:10:24+09:00
Subject: Re: How can i do 'foreach (reverse sort { $hasref->{$a} <=> $hasref->{$b} } keys %{$hasref})..' in ruby

Aleksandar Lazic <al-rubylang@none.at> wrote:
> Hi,
>
> I'am new with ruby and want to migrate some of my perlscripts to ruby
> ;-).
> I have a problem with the 'reverse sort' of values of a hashref and
> hope that sombody can help me or point me to the right way ;-)
>
> I have found the a nice answer
> http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/30322
>
> and have try the follwoing commands:
>
> clients.values.sort{|a,b| a[1] <=> b[1]}.each {|k,v|
>    puts "#{k} => #{v}"
> }
>
> clients.values.sort.reverse.each { |k|
>  puts "#{k}"
> }

Both of these sort values only!

> but it looks to me that sort give me only a array back.

Yes, it does - even if you sort the hash.  But that's natural as a Hash has 
no order so returning a Hash would not make sense.

> Here my perl code which i want to translate:
>
> ---
> foreach (reverse sort { $hasref->{$a} <=> $hasref->{$b} } keys
>  %{$hasref}){ printf("% 7i %s\n",$hasref->{$_},      $_);
>                     #^^^^^^^Key output  ^^value output
> }

If you want to reverse sort a Hash by values you can do

sorted = hash.sort {|(k1,v1),(k2,v2)| v2 <=> v1}

You can iterate "sorted" like a hash:

sorted.each {|k,v| print key, " => ", value, "\n"}

In some cases you can use sort_by:

irb(main):001:0> {1=>2,3=>4}.sort_by {|k,v| -v}
=> [[3, 4], [1, 2]]

Kind regards

    robert