ahem/lib/ahem/environment.rb

class Environment
  attr_reader :data

  def initialize(parent = nil)
    @data = Hash.new

    CORE.each { |k, v| @data[k.to_s] = v }

    parent.data.each { |k, v| @data[k] = v } unless parent.nil?
  end

  def get(name)
    if @data.has_key?(name)
      @data[name]
    else
      raise "Undefined variable #{name}"
    end
  end

  def set(name, value)
    @data[name] = value
  end
end