# Creates a method that requires to be overridding.
# If it not overridden and called upon a TypeError
# will be raised.
#
#  class C
#    abstract :a
#  end
#
#  c = C.new
#  c.a  #=> Error: undefined abstraction #a
#
class Module
  def abstract( *sym )
    sym.each { |s|
      define_method( s ) { raise TypeError, "undefined abstraction ##{s}" }
    }
  end
end



#  _____         _
# |_   _|__  ___| |_
#   | |/ _ \/ __| __|
#   | |  __/\__ \ |_
#   |_|\___||___/\__|
#
=begin test

  require 'test/unit'

  class TCModule < Test::Unit::TestCase

    class Aq
      abstract :q
    end

    def test_001
      ac = Aq.new
      assert_raises( TypeError ) { ac.q }
    end

    def test_002
      ac = Class.new { abstract :q }.new
      assert_raises( TypeError ) { ac.q }
    end

  end

=end