218 Syntax Highlighting
Namo namah Rubyists,
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.
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
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.
Thank you Caleb for your solution to this week’s quiz!