Rubasteme

Simple Abstract Syntax Tree and a parser for Scheme written in Ruby.

It is intended to be used as a part of a Scheme implementation written in Ruby.

• Rubasteme is a set of classes to represent an AST for Scheme language.
  • Currently (in 0.1.0), it does support partially the language specification of Scheme.
• Rubasteme does not provide any features for lexical analysis.
  • Instead, it uses rbscmlex to execute lexical analysis of Scheme program.

Add this line to your application's Gemfile:

gem 'rubasteme'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install rubasteme

See the directory, examples. There are 2 small implementations of subset for Scheme language. Though both have very limited capabilities as Scheme interpreter, they can execute the following code:

(define (fact n)
  (define (fact-iter n r c)
    (if (< n c)
	r
	(fact-iter n (* r c) (+ c 1))))
  (fact-iter n 1 1))

(display (fact 10))
(display (fact 100))
(display (fact 1000))

(define (iota-iter result count start step)
  (if (zero? count)
      result
      (iota-iter (append result (list start))
		 (- count 1)
		 (+ start step)
		 step)))

(define (iota count start step)
  (iota-iter () count start step))

(display (iota 10 1 1))
(display (iota 10 1/9 11/99))

1. Save the above code in a file.
2. Run examples/mini_rus3 or examples/mini_sicp_scheme
3. Input (load "some_file.scm") after the prompt, then hit return key.

Or, input any arbitrary expressions after the prompt. Note that the current REPL does not support to input expression in multi-lines. Each expression must be input entirely in a single line.

It is intended to show how to use Ruby classes of AST nodes.

It is intended to show how to use AST nodes those are represented as "tagged Array."

• empty list
• boolean
• identifier
• character
• string
• number
• program
• list
• quotation
• procedure call
• lambda expression
• conditional
• assignment
• identifier definition
• cond
• and
• or
• when
• unless
• let
• let*
• letrec
• letrec*
• do

• Add more documentation.
• Implement more types.
• Re-factor code.

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/mnbi/rubasteme.

The gem is available as open source under the terms of the MIT License.