From: Logan Capaldo <logancapaldo@...>
Date: 2007-01-22T13:33:13+09:00
Subject: Re: Tricky: converting path into a Hash

On Mon, Jan 22, 2007 at 01:10:08PM +0900, Ken Bloom wrote:
> 
> Then the inject trick becomes
> 
> pr = lambda {|h,k| h[k] = Hash.new(&pr)}
> z=Hash.new(&pr)
> s = "a/b/c"
> s.split("/").inject(z){|ha,co| ha[co]}
> s = "a/b/d"
> s.split("/").inject(z){|ha,co| ha[co]}
> s = "a/d/e"
> s.split("/").inject(z){|ha,co| ha[co]}
> s = "c/a/t"
> s.split("/").inject(z){|ha,co| ha[co]}
> p z
> 
> For some reason you can't name the hash h, otherwise the parameter
> assignment in the proc will override it. Why is that, and is there any way
> to avoid it?
Same reason as:

h = 3
lambda { h = "three" }.call
p h # prints "three"

Block arguments act like assignment. This can be seen in pathological
examples like lambda { |$a_global| ... } and lambda { |@an_ivar| ... }