A syntax highlighting a library for Ruby.


This is a simple syntax highlighting library for Ruby. It is a naive syntax analysis tool, meaning that it does not "understand" the syntaxes of the languages it processes, but merely does some semi-intelligent pattern matching.


There are primarily two uses for the Syntax library:

# Convert text from a supported syntax to a supported highlight format (like HTML). # Tokenize text in a supported syntax and process the tokens directly.

Highlighting a supported syntax

  require 'syntax/convertors/html'

  convertor = Syntax::Convertors::HTML.for_syntax "ruby"
  puts convertor.convert( "file.rb" ) )

The above snippet will emit HTML, using spans and CSS to indicate the different highlight "groups". (Sample CSS files are included in the "data" directory.)

Tokenize text

  require 'syntax'

  tokenizer = Syntax.load "ruby"
  tokenizer.tokenize( "file.rb" ) ) do |token|
    puts "group(#{}, #{token.instruction}) lexeme(#{token})"

Tokenizing is straightforward process. Each time a new token is discovered by the tokenizer, it is yielded to the given block.

  • is the lexical group to which the token belongs. Each supported syntax may have it’s own set of lexical groups.
  • token.instruction is an instruction used to determine how this token should be treated. It will be :none for normal tokens, :region_open if the token starts a nested region, and :region_close if it closes the last opened region.
  • token is itself a subclass of String, so you can use it just as you would a string. It represents the lexeme that was actually parsed.