From: Wilson Bilkovich <wilsonb@...>
Date: 2005-12-10T04:37:26+09:00
Subject: Re: new to Ruby - pls help in translating this

Or, something else to think about.. shamelessly borrowed from this
mailing list a month or so ago..
Wrapped in lame 'gets' code to let you play with it at the command
line.  I presume you'd actually do something cooler with STDIN or a
filename.

class Array
  def dups
     h, d = {}, []; each{|e| h[e] ? (d << h.delete(e)) : (h[e] = e)}; d
  end
end
numbers = []
while n = STDIN.gets.chomp
  break if n == ''
  numbers << n
end
puts numbers.dups

I love reopening Array.

--Wilson.

On 12/9/05, Sam Dela Cruz <sam.dela.cruz@philips.com> wrote:
> Hi,
>
> I'm starting to use Ruby in one of my projects at work.  I'm coming from a
> Perl background.
> In my project I would need to parse a list of numbers (thousands of them)
> and then return the duplicates.  In perl, I can do this:
>
> ##### Perl code
> %hash = {};
> while (<>)
> {
>     chomp;
>         $hash{$_}++;
> }
>
> foreach my $key (sort keys %hash)
> {
>     print "$key: $hash{$key}\n" if ($hash{$key} > 1);
> }
>
> I tried to translate this in Ruby, but could not find en equivalent of
> $hash{$_}++, this is auto increment.
> Can somebody tell me how this is to be done in Ruby?  Or maybe the Ruby
> way on how to attack this whole thing.  Thanks.
>
> Regards,
> Sam
>