Grammy: Ruby Recursive Descent Parser Generator

Grammy is a very small recursive descent parser generator framework written in ruby. It has several similarities with boost::spirit.

Short example: g = Grammy.define :letters do rule lower: 'a'..'z' rule upper: 'A'..'Z' rule letter: :lower | :upper start word: +:letter end

You can use the defined grammar to parse strings:

result = g.parse("ALongWord") result.full_match? #=> true result.to_image("test") # creates a .png with graphviz, graphviz is required for that

An example image (not for this grammar):

Grammy supports:

• Most EBNF features: Sequences, Repetition, Alternatives, Optional rules
• Shortcut for lists: list and list?
• Skipping of characters: comments, whitespaces between words
• Generation of an AST. Most unused tokens can be removed automatically.
• AST can be written to an image file with help of graphviz.

You can get grammy at github: Grammy on github

There is also a more detailed description there.