Package for representing formal grammars. Contains algorithms to work with a grammars and parse them.
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
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 == 16You can read more about the library in the doc directory.
You can view some examples in the examples directory.
Author: Patrik Valkovič
Licence: MIT
