gistfile1.rb

class SomeClass < ActiveRecord::Base
  def object_from_yaml_with_dmatrix_support(string)
    if string.is_a?(String) && string =~ /^Linalg\:\:DMatrix/
      eval string
    else
      object_from_yaml_without_dmatrix_support(string)
    end
  end
  alias_method_chain :object_from_yaml, :dmatrix_support
end

class Linalg::DMatrix
  def to_yaml
    "Linalg::DMatrix#{to_a.inspect}"
  end
end