Contents

require_relative 'state_set'
require_relative 'parse_state'

module Rley # This module is used as a namespace
  module Parser # This module is used as a namespace
    # Also called a parse table
    # A one-dimensional array with n + 1 entries (n = number of input tokens).
    class Chart
      attr_reader(:state_sets)

      def initialize(startDottedItem, tokenCount)
        @state_sets = Array.new(tokenCount + 1) { |_| StateSet.new }
        push_state(startDottedItem, 0, 0)
      end

      # The dotted item/rule used to seed the parse chart.
      # It corresponds to the start production and a dot placed
      # at the beginning of the rhs
      def start_dotted_rule()
        return self[0].states.first.dotted_rule
      end

      # Access the state set at given position
      def [](index)
        return state_sets[index]
      end
      
      # Return the index value of the last non-empty state set.
      def last_index()
        first_empty =  state_sets.find_index(&:empty?)
        if first_empty.nil?
          index = state_sets.size - 1
        else
          index = first_empty == 0 ? 0 : first_empty - 1
        end
        
        return index
      end

      # Push a parse state for the chart entry with given index
      def push_state(aDottedItem, anOrigin, anIndex)
        new_state = ParseState.new(aDottedItem, anOrigin)
        self[anIndex].push_state(new_state)
      end
    end # class
  end # module
end # module

# End of file

Version data entries

3 entries across 3 versions & 1 rubygems

Version	Path
rley-0.2.03	lib/rley/parser/chart.rb
rley-0.2.02	lib/rley/parser/chart.rb
rley-0.2.01	lib/rley/parser/chart.rb