igordejanovic / Parglare

.. image:: https://raw.githubusercontent.com/igordejanovic/parglare/master/docs/images/parglare-logo.png

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A pure Python scannerless LR/GLR parser.

For more information see the docs <http://www.igordejanovic.net/parglare/>_.

Quick intro

This is just a small example to get the general idea. This example shows how to parse and evaluate expressions with 5 operations with different priority and associativity. Evaluation is done using semantic/reduction actions.

The whole expression evaluator is done in under 30 lines of code!

.. code:: python

from parglare import Parser, Grammar

grammar = r"""
E: E '+' E  {left, 1}
 | E '-' E  {left, 1}
 | E '*' E  {left, 2}
 | E '/' E  {left, 2}
 | E '^' E  {right, 3}
 | '(' E ')'
 | number;

terminals
number: /\d+(\.\d+)?/;
"""

actions = {
    "E": [lambda _, n: n[0] + n[2],
          lambda _, n: n[0] - n[2],
          lambda _, n: n[0] * n[2],
          lambda _, n: n[0] / n[2],
          lambda _, n: n[0] ** n[2],
          lambda _, n: n[1],
          lambda _, n: n[0]],
    "number": lambda _, value: float(value),
}

g = Grammar.from_string(grammar)
parser = Parser(g, debug=True, actions=actions)

result = parser.parse("34 + 4.6 / 2 * 4^2^2 + 78")

print("Result = ", result)

# Output
# -- Debugging/tracing output with detailed info about grammar, productions,
# -- terminals and nonterminals, DFA states, parsing progress,
# -- and at the end of the output:
# Result = 700.8

Installation

• Stable version:

.. code:: shell

$ pip install parglare

• Development version:

.. code:: shell

$ git clone [email protected]:igordejanovic/parglare.git
$ pip install -e parglare

License

MIT

Python versions

Tested with 3.4-3.8

Credits

Initial layout/content of this package was created with Cookiecutter <https://github.com/audreyr/cookiecutter>_ and the audreyr/cookiecutter-pypackage <https://github.com/audreyr/cookiecutter-pypackage>_ project template.

.. |build-status| image:: https://travis-ci.org/igordejanovic/parglare.svg?branch=master :target: https://travis-ci.org/igordejanovic/parglare

.. |coverage| image:: https://coveralls.io/repos/github/igordejanovic/parglare/badge.svg?branch=master :target: https://coveralls.io/github/igordejanovic/parglare?branch=master

.. |docs| image:: https://img.shields.io/badge/docs-latest-green.svg :target: http://igordejanovic.net/parglare/latest/

.. |status| image:: https://img.shields.io/pypi/status/parglare.svg

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.. |python-versions| image:: https://img.shields.io/pypi/pyversions/parglare.svg