grammpy 2.1.1

Parsing library with all required tools to parse context-free grammars.

grammpy

Package for representing formal grammars. Contains algorithms to work with a grammars and parse them.

Installation

If you are using pip, simple run following command.

pip install grammpy

You can install the package from the repository as well.

git clone https://github.com/PatrikValkovic/grammpy.git
cd grammpy
python setup.py install

Usage

Defining a grammar doesn't require special tools anymore. All what you need is just an IDE and you have the full support.

Let's define grammar using standard Python objects instead.

from grammpy import *
from grammpy.transforms import ContextFree, InverseContextFree
from grammpy.parsers import cyk


class Number:
    def __init__(self, value):
        self.value = value
    def __hash__(self):
        return hash(Number)


class PlusNonterminal(Nonterminal):
    @property
    def value(self):
        return self.to_rule.get_value()


class PlusRule(Rule):
    rule = ([PlusNonterminal], [PlusNonterminal, '+', PlusNonterminal])
    def get_value(self):
        child1 = self.to_symbols[0]
        child2 = self.to_symbols[2]
        return child1.value + child2.value


class RewriteRule(Rule):
    fromSymbol = PlusNonterminal
    toSymbol = Number
    def get_value(self):
        return self.to_symbols[0].s.value


g = Grammar(terminals=[Number, '+'],
            nonterminals=[PlusNonterminal],
            rules=[PlusRule, RewriteRule],
            start_symbol=PlusNonterminal)
ContextFree.prepare_for_cyk(g, inplace=True)
root = cyk(g, [Number(5), '+', Number(3), '+' , Number(8)])
root = InverseContextFree.reverse_cyk_transforms(root)
assert root.value == 16

Documentation

You can read more about the library in the doc directory.

Examples

You can view some examples in the examples directory.

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Author: Patrik Valkovič

Licence: MIT