Parsing Expressions for Ruby
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~* Citrus *~ Parsing Expressions for Ruby Citrus is a compact and powerful parsing library for Ruby that combines the elegance and expressiveness of the language with the simplicity and power of parsing expression grammars. Citrus grammars look very much like Treetop grammars but take a completely different approach. Instead of generating parsers from your grammars, Citrus evaluates grammars and rules in memory as Ruby modules. In fact, you can even define your grammars as Ruby modules in the first place, entirely skipping the parsing/evaluation step. Terminals are represented as either strings or regular expressions. Support for sequences, choices, labels, repetition, and lookahead (both positive and negative) are all included, as well as character classes and the dot-matches- anything symbol. To try it out, fire up an IRB session from the root of the project and run one of the examples. $ irb -Ilib > require 'citrus' => true > Citrus.load 'examples/calc' => [Calc] > match = Calc.parse '1 + 5' => #<Citrus::Match ... > match.value => 6 Be sure to try requiring `citrus/debug' (instead of just `citrus') if you'd like some better visualization of the match results. The code base is very small and it's well-documented and tested, so it should be fairly easy to understand for anyone who is familiar with parsing expressions. ** Links ** http://pdos.csail.mit.edu/~baford/packrat/ http://en.wikipedia.org/wiki/Parsing_expression_grammar http://treetop.rubyforge.org/index.html ** Installation ** Via RubyGems: $ sudo gem install citrus From a local copy: $ git clone git://github.com/mjijackson/citrus.git $ cd citrus $ rake package && sudo rake install ** License ** Copyright 2010 Michael Jackson Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.