Module: Pushdown::Automaton::InstanceMethods

Defined in:
lib/pushdown/automaton.rb

Overview

A mixin to add instance methods for setting up pushdown states.

Instance Method Summary collapse

Instance Method Details

#handle_pushdown_result(stack, result, name) ⇒ Object

The body of the event handler, called by the #handle_name_event.



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# File 'lib/pushdown/automaton.rb', line 62

def handle_pushdown_result( stack, result, name )
  if result.is_a?( Symbol )
    current_state = stack.last
    result = current_state.transition( result, self, name )
  end

  if result.is_a?( Pushdown::Transition )
    new_stack = result.apply( stack )
    stack.replace( new_stack )
  end

  return result
end

#initialize ⇒ Object

Overload the initializer to push the initial state object for any pushdown states.



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# File 'lib/pushdown/automaton.rb', line 37

def initialize( * )
  super if defined?( super )

  self.class.pushdown_states.each do |name, config|
    self.log.debug "Pushing initial %s" % [ name ]

    state_class = self.class.public_send( "initial_#{name}" ) or
      raise "unset initial_%s while pushing initial state" % [ name ]

    data = if self.respond_to?( "initial_#{name}_data" )
        self.public_send( "initial_#{name}_data" )
      else
        nil
      end

    self.log.info "Pushing an instance of %p as the initial state." % [ state_class ]
    transition = Pushdown::Transition.create( :push, :initial, state_class, data )
    self.log.debug " applying %p to an new empty stack" % [ transition ]
    stack = transition.apply( [] )
    self.instance_variable_set( "@#{name}_stack", stack )
  end
end