Class: Aurum::Lexer

Inherits:
Object
  • Object
show all
Defined in:
lib/aurum/engine.rb

Instance Method Summary collapse

Constructor Details

#initialize(table, accepts, lexical_states, input) ⇒ Lexer

Returns a new instance of Lexer.



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# File 'lib/aurum/engine.rb', line 32

def initialize table, accepts, lexical_states, input
	@table, @accepts, @lexical_states, @input  = table, accepts, lexical_states, input			 
	shift_to :initial 
end

Instance Method Details

#goto(state, input) ⇒ Object 



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# File 'lib/aurum/engine.rb', line 63

def goto state, input
	return nil unless input
	next_state = @table[state].find {|tran| tran.symbols.include?(input)} 
	next_state ? next_state.destination : nil
end

#next_symbol ⇒ Object 



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# File 'lib/aurum/engine.rb', line 37

def next_symbol
	return Aurum::EOF if @input.eof?
	@recognized, lexeme, @pushback_symbol = @pushback_symbol, '', nil
	until @recognized
		next_state, char = @start_state, nil
		while next_state
			lexeme << char if char
			state, char = next_state, @input.get_char
			next_state = goto state, char 		
		end				
		@input.pushback char
		return Unknown unless actions = @accepts[state]
		if actions.first == IgnoreAction
			lexeme = ''
		else
			actions.first.execute self, lexeme
		end					 				
	end
	@recognized.value = lexeme unless @recognized.value 
	@recognized			
end

#pushback(symbol) ⇒ Object 



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# File 'lib/aurum/engine.rb', line 59

def pushback symbol
	@pushback_symbol = symbol
end

#recognize(token) ⇒ Object 



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# File 'lib/aurum/engine.rb', line 73

def recognize token
	@recognized = Aurum::Symbol.new token, true
end

#shift_to(state) ⇒ Object 



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# File 'lib/aurum/engine.rb', line 69

def shift_to state
	@start_state = goto 0, -@lexical_states.index(state)-1
end