Class: Grammar

Inherits:
Object show all
Defined in:
lib/rpdf2txt-rockit/grammar.rb

Defined Under Namespace

Classes: EpsilonTokenType

Constant Summary collapse

EpsilonToken = 
EpsilonTokenType.new

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name = nil, productions = [], tokens = [], priorities = nil, startSymbol = nil, exports = []) ⇒ Grammar

Returns a new instance of Grammar.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 493

def initialize(name = nil, productions = [], tokens = [], 
 priorities = nil,
 startSymbol = nil, exports = [])
  # NOTE! Beware that the EofToken below wont get a unique index number!!
  @eof_terminal = EofToken.new
  @name, @tokens, @alternatives = name, [@eof_terminal], Hash.new
  @priorities = priorities || ProductionPriorities.new
  @nonterminals = Array.new
  add_tokens(tokens)
  clear_productions
  add_productions(productions)
  init_start_symbol(startSymbol)
  @exports = exports
end

Instance Attribute Details

#eof_terminal ⇒ Object (readonly)

Returns the value of attribute eof_terminal.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 489

def eof_terminal
  @eof_terminal
end

#exports ⇒ Object (readonly)

Returns the value of attribute exports.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 488

def exports
  @exports
end

#name ⇒ Object

Returns the value of attribute name.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 490

def name
  @name
end

#original_start_symbol ⇒ Object (readonly)

Returns the value of attribute original_start_symbol.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 489

def original_start_symbol
  @original_start_symbol
end

#priorities ⇒ Object (readonly)

Returns the value of attribute priorities.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 488

def priorities
  @priorities
end

#productions ⇒ Object (readonly)

Returns the value of attribute productions.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 488

def productions
  @productions
end

#start_symbol ⇒ Object (readonly)

Returns the value of attribute start_symbol.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 488

def start_symbol
  @start_symbol
end

#tokens ⇒ Object (readonly) Also known as: terminals

Returns the value of attribute tokens.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 488

def tokens
  @tokens
end

Class Method Details

.epsilon ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 593

def Grammar.epsilon
  EpsilonToken
end

Instance Method Details

#+(otherGrammar) ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 555

def +(otherGrammar)
  # NOTE: Maybe check for and/or handle naming conflicts?
  add_tokens(otherGrammar.tokens)
  add_productions(otherGrammar.productions)
  otherGrammar.exports.each {|e| @exports.push(e)}
  self
end

#add_production(production) ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 541

def add_production(production)
  unless @productions.include?(production)
    add_unique_symbols(production)
    @productions.push production
    nt = production.nonterminal
    unless @alternatives[nt.name]
	@alternatives[nt.name] = [production]
    else
	@alternatives[nt.name].push production
    end
  end
  @start_symbol = production.nonterminal unless @start_symbol
end

#add_token(token) ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 521

def add_token(token)
  @tokens.push token unless @tokens.include?(token)
end

#add_unique_symbols(production) ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 525

def add_unique_symbols(production)
  production.elements = production.elements.map {|e| unique_symbol(e)}
  production.nonterminal = unique_symbol(production.nonterminal)
end

#alternatives(nonterminal) ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 508

def alternatives(nonterminal)
  @alternatives[nonterminal.name]
end

#augment ⇒ Object

Augment the grammar by adding new start symbol and production from it to previous start symbol. The added production gets index 0.



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 599

def augment
  return true if augmented?
  @original_start_symbol = self.start_symbol
  # Add prim's until unique nonterminal name
  new_name = @original_start_symbol.name + "'"
  while nonterminals.collect{|nt| nt.name}.include?(new_name)
    new_name += "'"
  end
  @start_symbol = NonTerminal.new(new_name)
  add_production(p = Production.new(@start_symbol, [@original_start_symbol]))
  # Make sure its on top
  @productions.delete p
  @productions.unshift p
  @augmented = true
end

#augmented? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rpdf2txt-rockit/grammar.rb', line 569

def augmented?
  @augmented ? true : false
end

#inspect ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 573

def inspect
  str = "Grammar #{@name}\n"
  str += "Start symbol: #{@start_symbol.inspect}\n" if @start_symbol
  str += "Tokens:\n" + @tokens.map{|t| "  " + t.inspect}.join("\n")
  str += "\nProductions:\n"
  @productions.each do |prod|
    str += "  " + prod.inspect + "\n"
  end
  str
end

#nonterminals(includeStartSymbol = true) ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 563

def nonterminals(includeStartSymbol = true)
  nts = (@productions.map {|p| p.nonterminal}).equality_uniq
  nts.delete(@start_symbol) unless includeStartSymbol
  nts
end

#normalize ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 512

def normalize
  old_productions = @productions
  clear_productions
  old_productions.each do |production|
    add_productions(production.normalize)
  end
  self
end

#unaugment ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 615

def unaugment
  return false unless augmented?
  @start_symbol = @original_start_symbol
  @productions.shift
  @augmented = false
end

#unique_symbol(symbol) ⇒ Object 



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# File 'lib/rpdf2txt-rockit/grammar.rb', line 530

def unique_symbol(symbol)
  existing_symbol = (@tokens + @nonterminals).detect {|e| e==symbol}
  if not existing_symbol
    add_token(symbol) if symbol.kind_of?(Token)
    @nonterminals.push(symbol) if symbol.kind_of?(NonTerminal)
    return symbol
  else
    return existing_symbol
  end
end