[QUIZ] Syntax Highlighting (#218)

ruby-talk
2

This was a fun little quiz. Of course, I cheated like mad. (I think
that was the point, tho.) My entry uses RubyLexer, my own stand-alone
lexer for ruby. It'll be interesting to see what other submissions
look like.

coloruby.rb (2.3 KB)

···

On 8/23/09, Daniel Moore <yahivin@gmail.com> wrote:

This week's quiz is to write a syntax highlighter. Your program or
method will take as input unadorned Ruby code and return marked-up
code. Different syntactical elements of the code should have different
styles. As an additional challenge you may wish to indicate syntax
errors at the point in which they occur in the code. You may choose
any output style that you like. If you are unsure of what to use to
colorize output, then check out Term::ANSIColor[1].

3

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