Class: Aspen::CustomGrammar::Lexer

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

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.tokenize(code, env = {}) ⇒ Object 



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# File 'lib/aspen/custom_grammar/lexer.rb', line 6

def self.tokenize(code, env={})
  new.tokenize(code, env)
end

Instance Method Details

#no_match(scanner, state) ⇒ Object

Raises:



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# File 'lib/aspen/custom_grammar/lexer.rb', line 69

def no_match(scanner, state)
  raise Aspen::LexError,
          Aspen::Errors.messages(:unexpected_token, scanner, state)
end

#pop_state ⇒ Object 



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# File 'lib/aspen/custom_grammar/lexer.rb', line 65

def pop_state
  stack.pop
end

#push_state(state) ⇒ Object 



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# File 'lib/aspen/custom_grammar/lexer.rb', line 61

def push_state(state)
  stack.push(state)
end

#stack ⇒ Object 



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# File 'lib/aspen/custom_grammar/lexer.rb', line 53

def stack
  @stack ||= []
end

#state ⇒ Object 



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# File 'lib/aspen/custom_grammar/lexer.rb', line 57

def state
  stack.last || :default
end

#tokenize(code, env = {}) ⇒ Object 



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# File 'lib/aspen/custom_grammar/lexer.rb', line 10

def tokenize(code, env={})
  scanner = StringScanner.new(code)
  tokens = []

  # puts "tokens: #{tokens} | state: #{state} | stack: #{stack}"

  until scanner.eos?
    case state
    when :default then
      if scanner.scan(/\(/)
        tokens << [:OPEN_PARENS]
        push_state :capture_segment
      elsif scanner.scan(/[[[:alnum:]][[:blank:]]\!"\#$%&'*+,\-.\/:;<=>?@\[\\\]^_‘\{\|\}~]+/)
        tokens << [:BARE, scanner.matched]
      else
        no_match(scanner, state)
      end

    when :capture_segment
      if scanner.scan(/\s+/)
        # NO OP
      elsif scanner.scan(/^(numeric|integer|float|string)/)
        tokens << [:TYPE, scanner.matched]
      elsif scanner.scan(Aspen::Lexer::PASCAL_CASE)
        tokens << [:TYPE, ["node", scanner.matched]]
      # TODO: This should only accept legal variable names, like `hello_01`
      elsif scanner.scan(/^\w+/)
        tokens << [:VAR_NAME, scanner.matched]
      elsif scanner.scan(/\)/)
        tokens << [:CLOSE_PARENS]
        pop_state
      else
        no_match(scanner, state)
      end

    else
      raise Aspen::LexError, "There is no matcher for state #{state.inspect}."
    end
  end

  tokens
end