From: Eric Mahurin <eric_mahurin@...>
Date: 2005-10-14T12:05:46+09:00
Subject: [ANN] grammar-0.5

Well, I'm finally doing a release of my grammar package:

http://rubyforge.org/projects/grammar/

I also released cursor-0.9 to go along with it:

http://rubyforge.org/projects/cursor/

Here are some of the features of it:

* BNF-like grammar written directly in Ruby (by overriding +,
|, *, &, ~, etc operators)

* lexer and parser grammars are specified in exactly the same
way - one parses characters and the other tokens

* can write a lexer-free parser

* may define tokens however is appropriate

* variety of Cursor options for connecting lexer to parser

* can put lexer and parser in different threads

* defaults to one character/token lookahead, but can extend to
arbitrary lookahead where needed

* autogenerates flattened code by using a macro-like facility

* ruby actions easily specified in blocks

* lots of convienent Grammar methods to combine and manipulate
grammars


TODO:

* error reporting needs work.  File/line/column numbers is
needed

* Cursor::Producer (multithreaded lexer cursor) needs some
love.  It doesn't have a very robut interface.

* various small API changes.  need more examples to see what
would be good to have.

* better testing.  only have partial random testing.


I also have to samples that you can look at:

- tcl interpreter: a complete tcl parser (no lexer needed) and
interpreter written in under 150 lines of ruby code.  The
example fact.tcl shows a recursive proc being defined and used
in tcl.

- infix 2 postfix expression converter: shows a lexer and
parser and how they can be multi-threaded.  converts an infix
expression into a postfix expression (looks like Joy) returned
in a simple array.



	
		
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