--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/1-Ruby/tree.rb	Sat Jan 07 20:36:33 2017 +0000
@@ -0,0 +1,36 @@
+#---
+# Excerpted from "Seven Languages in Seven Weeks",
+# published by The Pragmatic Bookshelf.
+# Copyrights apply to this code. It may not be used to create training material, 
+# courses, books, articles, and the like. Contact us if you are in doubt.
+# We make no guarantees that this code is fit for any purpose. 
+# Visit http://www.pragmaticprogrammer.com/titles/btlang for more book information.
+#---
+class Tree
+  attr_accessor :children, :node_name
+  
+  def initialize(name, children=[])
+    @children = children
+    @node_name = name
+  end
+  
+  def visit_all(&block)
+    visit &block
+    children.each {|c| c.visit_all &block}
+  end
+  
+  def visit(&block)
+    block.call self
+  end
+end
+
+ruby_tree = Tree.new( "Ruby", 
+  [Tree.new("Reia"), 
+   Tree.new("MacRuby")] )
+
+puts "Visiting a node"
+ruby_tree.visit {|node| puts node.node_name}
+puts
+
+puts "visiting entire tree"
+ruby_tree.visit_all {|node| puts node.node_name}