From: Dustin Barker <dustin.barker@...>
Date: 2008-06-11T05:02:06+09:00
Subject: Re: Basic Tree Data Structure


No problem - so try out this snippet:

t = Tree.new("a")
t1 = t << "b"
t1 << "c"
t << "d"

class Tree
  def each
    yield value
    @children.each do |child_node|
      child_node.each { |e| yield "node:#{value} yields:#{e}" }
    end
  end
end

t.each { |x| puts "each:#{x}" }

here's some annotated output:

each:a                                                        # (a)  
yield value
each:node:a yields:b                               # (b) yield value - 
 > (a) yield e
each:node:a yields:node:b yields:c      # (c) yield value -> (b) yield  
e -> (a) yield e
each:node:a yields:d                               # (d) yield value - 
 > (a) yield e

Seems like you're traversing correctly, I think the 1,2,3 output  
might've been confusing. The output of this snippet illustrates how  
the calls stack up - each yield returns to the caller, which in turn  
yields to it's caller, and so on.

-Dustin

On Jun 10, 2008, at 3:04 PM, Justin To wrote:

> Thanks Dustin, that clarifies one bit of the confusion, but I'm still
> puzzled:
>
> Output: Parent
> in child node
> 3 Parent
> Output: Child 1
> in child node
> 3 Child 1
> 3 Parent   # Q1: Why does it go through the Parent again?
> Output: Grandchild 1.1
>
> class Tree
>  def each
>    puts "1"
>    yield value   # Q2: Which block does this invoke?
>    puts "2"
>    @children.each do |child_node|
>      puts "in child_node"
>        child_node.each { |e| puts "3"; yield e;  } # Q3: Which block
> does this
>                                                    #     yield invoke?
>      end
>  end
> end
>
> t.each { |x| puts "t.each"; puts x }
>
> I'm trying hard to understand!! =D Thanks for the help!
> -- 
> Posted via http://www.ruby-forum.com/.
>