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copied!<p>It started off as this:</p> <pre><code>class Tree include Comparable attr_reader :data # Create a new node with one initial data element def initialize(data=nil) @data = data end # Spaceship operator. Comparable uses this to generate # <, <=, ==, =>, >, and between? def <=>(other) @data.to_s <=> other.data.to_s end # Insert an object into the subtree including and under this Node. # First choose whether to insert into the left or right subtree, # then either create a new node or insert into the existing node at # the head of that subtree. def insert(data) if !@data @data = data else node = (data.to_s < @data.to_s) ? :@left : :@right create_or_insert_node(node, data) end end # Sum all the numerical values in this tree. If this data object is a # descendant of Numeric, add @data to the sum, then descend into both subtrees. def total sum = 0 sum += @data if (@data.is_a? Numeric) sum += [@left, @right].map{|e| e.total rescue 0}.inject(0){|a,v|a+v} sum end # Convert this subtree to a String. # Format is: <tt>\<data,left_subtree,right_subtree></tt>. # Non-existant Nodes are printed as <tt>\<></tt>. def to_s subtree = lambda do |tree| tree.to_s.empty? ? "<>" : tree end "<#{@data},#{subtree[@left]},#{subtree[@right]}>" end private ############################################################ # Given a variable-as-symbol, insert data into the subtree incl. and under this node. def create_or_insert_node(nodename, data) if instance_variable_get(nodename).nil? instance_variable_set(nodename, Tree.new(data)) else instance_variable_get(nodename).insert(data) end end end </code></pre> <p>I think I actually broke it when I was shortening it down. The nine-line version doesn't quite work. I had fun regardless. :P</p> <p>This was my favourite part:</p> <pre><code>def initialize*d;@d,=d;end </code></pre> <p>This is acutally making use of parallel assignment to save a couple characters. You could expand this line to:</p> <pre><code>def initialize(*d) @d = d[0] end </code></pre>

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