Class: Item

Inherits:
Object show all
Includes:
Indexable
Defined in:
lib/rpdf2txt-rockit/parsetable_generation.rb

Constant Summary collapse

@@empty_array = 
Array.new

Instance Attribute Summary collapse

Attributes included from Indexable

#factory, #index_number

Instance Method Summary collapse

Constructor Details

#initialize(production, position, lookahead = nil, nextItem = nil) ⇒ Item

Returns a new instance of Item.



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 11

def initialize(production, position, lookahead = nil, nextItem = nil)
  @production, @position, @lookahead = production, position, lookahead
  @symbol = production.elements[position]
  @hash_value = [production, position, lookahead].hash
end

Instance Attribute Details

#lookahead ⇒ Object (readonly)

Returns the value of attribute lookahead.



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 9

def lookahead
  @lookahead
end

#position ⇒ Object (readonly)

Returns the value of attribute position.



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 9

def position
  @position
end

#production ⇒ Object (readonly)

Returns the value of attribute production.



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 9

def production
  @production
end

#symbol ⇒ Object (readonly)

Returns the value of attribute symbol.



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 9

def symbol
  @symbol
end

Instance Method Details

#calc_followers ⇒ Object 



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 21

def calc_followers
  return @@empty_array if position >= production.elements.length-1
  elements = production.elements[position+1..-1]
  followers = Array.new
  elements.each do |e|
    followers.push e
    return followers unless e.derives_epsilon?
  end
  followers
end

#direct_following_symbols ⇒ Object 



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 17

def direct_following_symbols
  @direct_following_symbols || (@direct_following_symbols = calc_followers)
end

#final? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 42

def final?
  next_item == nil
end

#inspect ⇒ Object 



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 54

def inspect
  endpos = ((@position >= production.elements.length) or 
     (@position == 0))
  production.nonterminal.inspect + "->" +
    inspect_elements(production.elements[0...@position]) +
    (endpos ? "." : " .") +
    inspect_elements(production.elements[@position..-1])
end

#lookahead_item(lookaheadSymbol) ⇒ Object 



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 50

def lookahead_item(lookaheadSymbol)
  make_new_item(production, position, lookaheadSymbol, next_item)
end

#next_item ⇒ Object 



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 46

def next_item
  @next_item || (@next_item = calc_next_item)
end

#suffix ⇒ Object 



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# File 'lib/rpdf2txt-rockit/parsetable_generation.rb', line 34

def suffix
  if position < production.elements.length-1
    production.elements[position+1..-1]
  else
    nil
  end
end