From: Joel VanderWerf <vjoel@...>
Date: 2007-01-22T10:46:00+09:00
Subject: Re: Tricky: converting path into a Hash

Robert MannI wrote:
> Hello!
> 
> 
> I am wondering if the mighty ruby crowd has a brilliant idea for a tricky
> problem I am solving.
> 
> I need to store a path as a tree in a hash.
> 
> Given:
> a/b/c
> 
> I want the Hash:
> { 'a' => { 'b' => { 'c' => { } } } }
> or written differently
> hsh['a']['b']['c'] = {}

This is a fairly standard idiom:

pr = proc {|h,k| h[k] = Hash.new(&pr)}

h = Hash.new(&pr)

h['a']['b']['c'] = {}

p h   # ==> {"a"=>{"b"=>{"c"=>{}}}}

For more discussion, search for "autovivify hash" on the list...

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