From: Robert MannI <robmnl@...>
Date: 2007-01-22T19:32:22+09:00
Subject: Re: Tricky: converting path into a Hash

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Gracias everyone!


I actually thought about the inject trick in bed at dawn but Ken Bloom's
solution is better for me, because it doesn't override any data once I add
paths to the tree.

Grateful for all the smart answers.


 - Rob the rabbit

On 1/22/07, Logan Capaldo <logancapaldo@gmail.com> wrote:
>
> 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| ... }
>
>
>
>

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