From: Joel VanderWerf <vjoel@...>
Date: 2005-05-26T07:27:33+09:00
Subject: Re: Multilevel hash

Joel VanderWerf wrote:
> aartist wrote:
> 
>> With perl it's easy to write:
>>
>> $Q{$date}{$song_played} += 1
>>
>> How I can accomplish the same thing with ruby?
>>
>> Thanks!
>>
>> http://pleac.sourceforge.net/pleac_ruby/index.html didn't help much
>> here.
>>
> 
> irb(main):001:0> mh = Hash.new {|h,k| h[k] = {} }
> => {}
> irb(main):002:0> mh[1][2] = 3
> => 3
> irb(main):003:0> mh
> => {1=>{2=>3}}

And if you want automatic zeros:

irb(main):010:0> mh0 = Hash.new {|h,k| h[k] = Hash.new(0)}
=> {}
irb(main):011:0> mh0[1][2] += 1
=> 1
irb(main):012:0> mh0
=> {1=>{2=>1}}