Example for issue 40

issue_40_testcase.rb

#!/usr/bin/env ruby

require 'wongi-engine'

engine = Wongi::Engine.create

engine.rule 'event_program' do
  for_all {
    fact :Event, 'program_name', 'Level 1 Coaching Certification v2'
  }
  do! {
    gen  :Event, 'type',         'version 2.0'
  }
end

engine << [:A,      'program_name', 'Level 1 Coaching Certification']

puts engine.select(:_, :_, :_)
puts '-----'

engine.retract [:A, 'program_name', 'Level 1 Coaching Certification']

engine << [:A,    'program_name','Level 1 Coaching Certification v2']
puts engine.select(:_, :_, :_)
puts '-----'

Fixed retract statement in revision 2.