From: Daniel Moore <yahivin@...>
Date: 2009-09-08T07:36:39+09:00
Subject: [QUIZ][SUMMARY] Syntax Highlighting (#218)

This week's quiz was solved by Caleb Clausen.

Caleb used the `RubyLexer` gem to parse a Ruby file given as a command
line argument. `Term::ANSIColor` is used to color the tokens.

    def coloruby file,fd=open(file)
      lexer=RubyLexer.new(file,fd)
      begin
        token=lexer.get1token
        print token.colorize
      end until RubyLexer::EoiToken===token
    ensure
      print Term::ANSIColor.reset
    end

The `coloruby` method uses `RubyLexer` to generate a stream of tokens.
Each token is then colorized and printed out. After all the tokens are
printed the color is reset with `Term::ANSIColor.reset` so that any
following text won't receive collateral colorization.

So how are these tokens colorized anyway? Caleb's solution opens up
the `RubyLexer` class and adds a `colorize` method to all tokens.
`Term::ANSIColor` is also included in the `Token` class so that all
the color methods are available as well.

    class Token
      include Term::ANSIColor

      def colorize
        color+ident.to_s
      end
    end

Each individual token class may define its own different color or
colorize method.

    class MethNameToken
      alias color green
    end

    class KeywordToken
      def colorize
        if /[^a-z]/i===ident
          yellow+ident
        else
          red+ident
        end
      end
    end

The end result is nice colorful Ruby code.[1]

Thank you Caleb for your solution to this week's quiz!

[Syntax Highlighting (#218) - Solutions][2]

[1]: http://rubyquiz.strd6.com/quizzes/218/colorized.png
[2]: http://rubyquiz.strd6.com/quizzes/218.tar.gz