Class: Liquid::Lexer

Inherits:
Object
  • Object
show all
Defined in:
lib/liquid/lexer.rb

Constant Summary collapse

SPECIALS = 
{
  '|'.freeze => :pipe,
  '.'.freeze => :dot,
  ':'.freeze => :colon,
  ','.freeze => :comma,
  '['.freeze => :open_square,
  ']'.freeze => :close_square,
  '('.freeze => :open_round,
  ')'.freeze => :close_round,
  '?'.freeze => :question,
  '-'.freeze => :dash
}.freeze
IDENTIFIER = 
/[a-zA-Z_][\w-]*\??/
SINGLE_STRING_LITERAL = 
/'[^\']*'/
DOUBLE_STRING_LITERAL = 
/"[^\"]*"/
NUMBER_LITERAL = 
/-?\d+(\.\d+)?/
DOTDOT = 
/\.\./
COMPARISON_OPERATOR = 
/==|!=|<>|<=?|>=?|contains(?=\s)/
WHITESPACE_OR_NOTHING = 
/\s*/

Instance Method Summary collapse

Constructor Details

#initialize(input) ⇒ Lexer

Returns a new instance of Lexer.



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# File 'lib/liquid/lexer.rb', line 24

def initialize(input)
  @ss = StringScanner.new(input)
end

Instance Method Details

#tokenize ⇒ Object 



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# File 'lib/liquid/lexer.rb', line 28

def tokenize
  @output = []

  until @ss.eos?
    @ss.skip(WHITESPACE_OR_NOTHING)
    break if @ss.eos?
    tok = case
    when t = @ss.scan(COMPARISON_OPERATOR) then [:comparison, t]
    when t = @ss.scan(SINGLE_STRING_LITERAL) then [:string, t]
    when t = @ss.scan(DOUBLE_STRING_LITERAL) then [:string, t]
    when t = @ss.scan(NUMBER_LITERAL) then [:number, t]
    when t = @ss.scan(IDENTIFIER) then [:id, t]
    when t = @ss.scan(DOTDOT) then [:dotdot, t]
    else
      c = @ss.getch
      if s = SPECIALS[c]
        [s, c]
      else
        raise SyntaxError, "Unexpected character #{c}"
      end
    end
    @output << tok
  end

  @output << [:end_of_string]
end