TatSu takes a grammar in a variation of EBNF as input, and outputs a memoizing PEG/Packrat parser in Python.
At least for the people who send me mail about a new language that they’re designing, the general advice is: do it to learn about how to write a compiler. Don’t have any expectations that anyone will use it, unless you hook up with some sort of organization in a position to push it hard. It’s a lottery, and some can buy a lot of the tickets. There are plenty of beautiful languages (more beautiful than C) that didn’t catch on. But someone does win the lottery, and doing a language at least teaches you something.
def WARNING(): return 'v4.4.0 is the last version of |TatSu| supporting Python 2.7'
竜 TatSu can compile a grammar stored in a string into a tatsu.grammars.Grammar object that can be used to parse any given input, much like the re module does with regular expressions, or it can generate a Python module that implements the parser.
$ pip install TatSu
Using the Tool
tatsu.compile(grammar, name=None, **kwargs)
Compiles the grammar and generates a model that can subsequently be used for parsing input with.
tatsu.parse(grammar, input, **kwargs)
Compiles the grammar and parses the given input producing an AST as result. The result is equivalent to calling:
model = compile(grammar) ast = model.parse(input)
Compiled grammars are cached for efficiency.
tatsu.to_python_sourcecode(grammar, name=None, filename=None, **kwargs)
Compiles the grammar to the Python sourcecode that implements the parser.
This is an example of how to use 竜 TatSu as a library:
GRAMMAR = ''' @@grammar::CALC start = expression $ ; expression = | expression '+' term | expression '-' term | term ; term = | term '*' factor | term '/' factor | factor ; factor = | '(' expression ')' | number ; number = /\d+/ ; ''' if __name__ == '__main__': import pprint import json from tatsu import parse from tatsu.util import asjson ast = parse(GRAMMAR, '3 + 5 * ( 10 - 20 )') print('# PPRINT') pprint.pprint(ast, indent=2, width=20) print() print('# JSON') print(json.dumps(asjson(ast), indent=2)) print()
竜 TatSu will use the first rule defined in the grammar as the start rule.
This is the output:
# PPRINT [ '3', '+', [ '5', '*', [ '10', '-', '20']]] # JSON [ "3", "+", [ "5", "*", [ "10", "-", "20" ] ] ]
For a detailed explanation of what 竜 TatSu is capable of, please see the documentation.
See the CHANGELOG for details.
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