From: Joel VanderWerf <vjoel@...>
Date: 2006-07-13T05:52:09+09:00
Subject: Re: multiple level hash assignment equivalence to perl

don mc wrote:
> Is there a succinct way in ruby to do a multiple level hash assignement? 
> I am more
> used to perl, which you can do something like
> 
> 
> $hp->{level1}->{level2} = 3
> 
> even if the first and second level had never existed below.

There's an autovivification trick, using the default proc of a hash (see 
ri default_proc):

irb(main):002:0> pr = proc {|h,k| h[k]=Hash.new(&pr) }
=> #<Proc:0x02c15618@(irb):2>
irb(main):003:0> h = Hash.new(&pr)
=> {}
irb(main):004:0> h[1][2][3][4] = 5
=> 5
irb(main):005:0> h
=> {1=>{2=>{3=>{4=>5}}}}

-- 
        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407