added useful_code dir

useful_code/ruby/util/tree_printer.rb

@@ -0,0 +1,49 @@
+module Util
+  class TreePrinter
+    attr_accessor :is_branch
+    attr_accessor :get_children
+    attr_accessor :format_node
+    attr_accessor :skip_root_node
+
+    def initialize
+      @arms = Hash.new("|   ")
+      @arms[""]  = ""
+      @arms["`"] = "    "
+      @out = ""
+      @is_branch    = proc{|node| node.has_children? }
+      @get_children = proc{|node| node.children}
+      @format_node  = proc{|node| node.to_s}
+      @skip_root_node = false
+    end
+
+    def visit(path, leader, tie, arm, node)
+      if(@root == node) && skip_root_node
+        # skip
+      else
+        node_str = @format_node.call(node)
+        @out << "#{leader}#{arm}#{tie}#{node_str}\n"
+      end
+      visitChildren(node, leader + @arms[arm])
+      @out
+    end
+
+    def visitChildren(path, leader)
+      kids = []
+      if(@root == path) && skip_root_node
+        kids = path
+      else
+        return unless @is_branch.call(path)
+        kids = @get_children.call(path)
+      end
+      return if kids.empty?
+      arms = Array.new(kids.length - 1, "|") << "`"
+      pairs = kids.zip(arms)
+      pairs.each { |e|  visit(path, leader, "-- ", e[1], e[0]) } 
+    end
+
+    def format(root)
+      @root = root
+      visit root, "", "", "", root 
+    end
+  end
+end