Jison generates bottom-up parsers in JavaScript. Its API is similar to Bison's, hence the name. It supports many of Bison's major features, plus some of its own. If you are new to parser generators such as Bison, and Context-free Grammars in general, a good introduction is found in the Bison manual. If you already know Bison, Jison should be easy to pickup.
A brief warning before proceeding: the API is ridiculously unstable right now. The goal is to mirror Bison where it makes sense, but we're not even there yet. Also, optimization has not been a main focus as of yet.
Briefly, Jison takes a JSON encoded grammar specification and outputs a JavaScript file capable of parsing the language described by that grammar specification. You can then use the generated script to parse inputs and accept, reject, or perform actions based on the input.
Jison can be installed for Narwhal using its bundled tusk command or for Node using npm
Using npm:
npm install jison
Using tusk:
tusk install jison
Clone the github repository for examples:
git clone git://github.com/zaach/jison.git
cd jison/examples
Now you're ready to generate some parsers:
jison calculator.jison
This will generate calculator.js in your current working directory. This file can be used to parse an input file, like so:
echo "2^32 / 1024" > testcalc
node calculator.js testcalc
This will print out 4194304.
You can generate parsers programatically from JavaScript as well. Assuming Jison is in your commonjs environment's load path:
// mygenerator.js
var Parser = require("jison").Parser;
// a grammar in JSON
var grammar = {
"lex": {
"rules": [
["\\s+", "/* skip whitespace */"],
["[a-f0-9]+", "return 'HEX';"]
]
},
"bnf": {
"hex_strings" :[ "hex_strings HEX",
"HEX" ]
}
};
var parser = new Parser(grammar);
// generate source, ready to be written to disk
var parserSource = parser.generate();
// you can also use the parser directly from memory
// returns true
parser.parse("adfe34bc e82a");
// throws lexical error
parser.parse("adfe34bc zxg");
For more information on creating grammars and using the generated parsers, read the documentation.
Fork the integration branch, make your changes, run tests and/or add tests then send a pull request.
Run tests with:
make test
Special thanks to Jarred Ligatti, Manuel E. Bermúdez
Copyright (c) 2009 Zachary Carter
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.