From: Ceri Storey <cez-misc.ruby-talk@...>
Date: 2004-04-04T18:11:35+09:00
Subject: Re: recursion w/ blocks; *this

On Sun, Apr 04, 2004 at 05:58:04PM +0900, Nicholas Paul Johnson wrote:
> Hello again,
> 
> First is, does Ruby have anything equivalent to C++'s `this' pointer?  
> I've tried the docs, but don't know what to look for other than 'this'...

Aye. You're looking for the 'self'. eg:
irb(main):001:0> self
=> main

> Second, if I were to write a method that accepts a block, and would like 
> to be able to recurse in that method while allowing each of the recursions 
> to use the same block, how would I do that?  

def a_method(arg, &block)
	if arg > 10
	    a_method(arg.succ, &block)
    end
end

More details here: http://rubycentral.com/book/tut_methods.html


> As an example, suppose I have a tree data structure (below), such that
> each node has two children: a and b.  I want to create an ``each'' method.  
> Ideally, I would yield with ``this,'' and then would recurse to ``each''
> on every child of that node.

class Node
	def initialize(left, right)
		@left = left
		@right = @right
	end

	def each(&block)
		block.call(self)
		@left.each(&block) if @left
		@right.each(&block) if @left
	end
end

-- 
Ceri Storey <cez@necrofish.org.uk>