Basic Genetic Programming From Collective Intelligence Book

class FWrapper
  
  attr_reader :function, :params, :name
  
  def initialize(function, params, name)
    @function = function
    @params = params
    @name = name
  end
  
end

class Node
  
  attr_reader :function, :children, :name
  
  def initialize(fw, children)
    @function = fw.function
    @name = fw.name
    @children = children
  end
  
  def evaluate(inp)
    results = children.inject([]) {|ary, n| ary << n.evaluate(inp)}
    function.call(results)
  end
  
  def display(indent=0)
    puts ' '*indent + name
    children.each {|c| c.display(indent+1)}
  end
  
end

class ParamNode
  
  attr_reader :idx
  
  def initialize(idx)
    @idx = idx
  end
  
  def evaluate(inp)
    inp[idx]
  end
  
  def display(indent=0)
    puts ' '*indent + idx.to_s
  end
  
end

class ConstNode
  
  attr_reader :v
  
  def initialize(v)
    @v = v
  end
  
  def evaluate(inp)
    v
  end
  
  def display(indent=0)
    puts ' '*indent + v.to_s
  end
  
end


addw = FWrapper.new(lambda {|x| x[0] + x[1]}, 2, 'add')
subw = FWrapper.new(lambda {|x| x[0] - x[1]}, 2, 'subtract')
mulw = FWrapper.new(lambda {|x| x[0] * x[1]}, 2, 'multiply')

iffunc = lambda do |x|
  if x[0] > 0
    return x[1]
  else
    return x[2]
  end
end

isgreater = lambda do |x|
  if x[0] > x[1]
    return 1
  else
    return 0
  end
end

ifw = FWrapper.new(iffunc, 3, 'if')
gtw = FWrapper.new(isgreater, 2, 'isgreater')

flist = [addw, subw, mulw, ifw, gtw]

example_tree = Node.new(ifw, [
              Node.new(gtw, [ParamNode.new(0), ConstNode.new(3)]),
              Node.new(addw, [ParamNode.new(1), ConstNode.new(5)]),
              Node.new(subw, [ParamNode.new(1), ConstNode.new(2)])
              ])

example_tree.display

puts example_tree.evaluate([5,3])