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A command line tool for Alessandro Warth's OMetaJS ( an object-oriented language for pattern matching )
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This project is a fork of OMetaJS by Alex Warth master branch.

It is also initially based on nodejs conversion written by Sergey Berezhnoy nodejs branch.


OMetaJS is a JavaScript implementation of OMeta, an object-oriented language for pattern matching.

To learn more:


The goal of this project is to provide a tool-chain tool for easily working with OMetaJS. ometajsnode allows one to specify grammar file, interpreter file, ( in future also compiler files/modules ), and program files via command line, and offers a number of options of execution such as parse mode, interpreter mode, and compile mode.

Work in progress

Incorporating compiler / code emitting code is going to get worked on soon. I'm not sure if packaging works with npm yet, but I'll get there. stdin input is not working yet.


Currently, parsing and interpreting works. See below walkthrough.

see usage via ./ometajsnode -h or ./ometajsnode --help

Parser example:

from the bin directory:

./ometajsnode -P -g ../examples/grammar_to_ir.ometajs --parser-root expr -o output.file ../examples/program.file ../examples/program2.file --debug

Let's breakdown that command step by step:

  • -P sets ometajsnode into Parse mode, which will essentially output the Abstract Syntax Tree for each of the programs
  • -g ../examples/grammar_to_ir.ometajs specifies the file containing ometajs grammar to use
  • --parser-root expr specifies 'expr' as the root element of the grammar for the parser to try to match
  • -o output.file specifies the file to which output will be written ( if -o is not present, output is directed to stdout )
  • ../examples/program.file ../examples/program2.file specifies two programs to process
  • --debug sets mode to debug, which will display a lot of information detailing the execution process

Combined parser and interpreter example:

from the bin directory:

./ometajsnode -I -g ../examples/grammar_and_interpreter.ometajs --interpreter-root expr -o output.file ../examples/program.file ../examples/program2.file --verbose

This command is similar to the one above with some differences:

  • -I sets ometajsnode into Interpret mode, which will actually interpret each of the programs and display the result
  • --interpreter-root expr similarly to --parser-root, this specifies the root element of the grammar for the interpreter to try to match
  • --verbose sets mode to verbose, which is not as detailed as debug, but will give you more detailed information

Parser to intermediate representation which then is interpreted example:

from the bin directory:

./ometajsnode -I -g ../examples/grammar_to_ir.ometajs --parser-root expr -i ../examples/interpreter.ometajs --interpreter-root interp -o output.file ../examples/program.file ../examples/program2.file --debug

We have little bit more going on here:

  • -i in addition to -g which specified the grammar file, we add an interpreter file that will work with the output of parsing according to grammar file
  • because we specified both a grammar and an interpreter, we need to provide both --parser-root and --interpreter-root


I welcome your input and feedback.


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