| Name | rply JSON |
| Version |
0.7.8
JSON |
| download |
| home_page | |
| Summary | A pure Python Lex/Yacc that works with RPython |
| upload_time | 2021-01-27 21:14:29 |
| maintainer | |
| docs_url | None |
| author | Alex Gaynor |
| requires_python | |
| license | BSD 3-Clause License |
| keywords |
|
| VCS |
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| bugtrack_url |
|
| requirements |
No requirements were recorded.
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|
RPLY
====
.. image:: https://secure.travis-ci.org/alex/rply.png
:target: https://travis-ci.org/alex/rply
Welcome to RPLY! A pure Python parser generator, that also works with RPython.
It is a more-or-less direct port of David Beazley's awesome PLY, with a new
public API, and RPython support.
You can find the documentation `online`_.
Basic API:
.. code:: python
from rply import ParserGenerator, LexerGenerator
from rply.token import BaseBox
lg = LexerGenerator()
# Add takes a rule name, and a regular expression that defines the rule.
lg.add("PLUS", r"\+")
lg.add("MINUS", r"-")
lg.add("NUMBER", r"\d+")
lg.ignore(r"\s+")
# This is a list of the token names. precedence is an optional list of
# tuples which specifies order of operation for avoiding ambiguity.
# precedence must be one of "left", "right", "nonassoc".
# cache_id is an optional string which specifies an ID to use for
# caching. It should *always* be safe to use caching,
# RPly will automatically detect when your grammar is
# changed and refresh the cache for you.
pg = ParserGenerator(["NUMBER", "PLUS", "MINUS"],
precedence=[("left", ['PLUS', 'MINUS'])], cache_id="myparser")
@pg.production("main : expr")
def main(p):
# p is a list, of each of the pieces on the right hand side of the
# grammar rule
return p[0]
@pg.production("expr : expr PLUS expr")
@pg.production("expr : expr MINUS expr")
def expr_op(p):
lhs = p[0].getint()
rhs = p[2].getint()
if p[1].gettokentype() == "PLUS":
return BoxInt(lhs + rhs)
elif p[1].gettokentype() == "MINUS":
return BoxInt(lhs - rhs)
else:
raise AssertionError("This is impossible, abort the time machine!")
@pg.production("expr : NUMBER")
def expr_num(p):
return BoxInt(int(p[0].getstr()))
lexer = lg.build()
parser = pg.build()
class BoxInt(BaseBox):
def __init__(self, value):
self.value = value
def getint(self):
return self.value
Then you can do:
.. code:: python
parser.parse(lexer.lex("1 + 3 - 2+12-32"))
You can also substitute your own lexer. A lexer is an object with a ``next()``
method that returns either the next token in sequence, or ``None`` if the token
stream has been exhausted.
Why do we have the boxes?
-------------------------
In RPython, like other statically typed languages, a variable must have a
specific type, we take advantage of polymorphism to keep values in a box so
that everything is statically typed. You can write whatever boxes you need for
your project.
If you don't intend to use your parser from RPython, and just want a cool pure
Python parser you can ignore all the box stuff and just return whatever you
like from each production method.
Error handling
--------------
By default, when a parsing error is encountered, an ``rply.ParsingError`` is
raised, it has a method ``getsourcepos()``, which returns an
``rply.token.SourcePosition`` object.
You may also provide an error handler, which, at the moment, must raise an
exception. It receives the ``Token`` object that the parser errored on.
.. code:: python
pg = ParserGenerator(...)
@pg.error
def error_handler(token):
raise ValueError("Ran into a %s where it wasn't expected" % token.gettokentype())
Python compatibility
--------------------
RPly is tested and known to work under Python 2.7, 3.4+, and PyPy. It is
also valid RPython for PyPy checkouts from ``6c642ae7a0ea`` onwards.
Links
-----
* `Source code and issue tracker <https://github.com/alex/rply/>`_
* `PyPI releases <https://pypi.python.org/pypi/rply>`_
* `Talk at PyCon US 2013: So you want to write an interpreter? <http://pyvideo.org/video/1694/so-you-want-to-write-an-interpreter>`_
.. _`online`: https://rply.readthedocs.io/
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"description": "RPLY\n====\n\n.. image:: https://secure.travis-ci.org/alex/rply.png\n :target: https://travis-ci.org/alex/rply\n\nWelcome to RPLY! A pure Python parser generator, that also works with RPython.\nIt is a more-or-less direct port of David Beazley's awesome PLY, with a new\npublic API, and RPython support.\n\nYou can find the documentation `online`_.\n\nBasic API:\n\n.. code:: python\n\n from rply import ParserGenerator, LexerGenerator\n from rply.token import BaseBox\n\n lg = LexerGenerator()\n # Add takes a rule name, and a regular expression that defines the rule.\n lg.add(\"PLUS\", r\"\\+\")\n lg.add(\"MINUS\", r\"-\")\n lg.add(\"NUMBER\", r\"\\d+\")\n\n lg.ignore(r\"\\s+\")\n\n # This is a list of the token names. precedence is an optional list of\n # tuples which specifies order of operation for avoiding ambiguity.\n # precedence must be one of \"left\", \"right\", \"nonassoc\".\n # cache_id is an optional string which specifies an ID to use for\n # caching. It should *always* be safe to use caching,\n # RPly will automatically detect when your grammar is\n # changed and refresh the cache for you.\n pg = ParserGenerator([\"NUMBER\", \"PLUS\", \"MINUS\"],\n precedence=[(\"left\", ['PLUS', 'MINUS'])], cache_id=\"myparser\")\n\n @pg.production(\"main : expr\")\n def main(p):\n # p is a list, of each of the pieces on the right hand side of the\n # grammar rule\n return p[0]\n\n @pg.production(\"expr : expr PLUS expr\")\n @pg.production(\"expr : expr MINUS expr\")\n def expr_op(p):\n lhs = p[0].getint()\n rhs = p[2].getint()\n if p[1].gettokentype() == \"PLUS\":\n return BoxInt(lhs + rhs)\n elif p[1].gettokentype() == \"MINUS\":\n return BoxInt(lhs - rhs)\n else:\n raise AssertionError(\"This is impossible, abort the time machine!\")\n\n @pg.production(\"expr : NUMBER\")\n def expr_num(p):\n return BoxInt(int(p[0].getstr()))\n\n lexer = lg.build()\n parser = pg.build()\n\n class BoxInt(BaseBox):\n def __init__(self, value):\n self.value = value\n\n def getint(self):\n return self.value\n\nThen you can do:\n\n.. code:: python\n\n parser.parse(lexer.lex(\"1 + 3 - 2+12-32\"))\n\nYou can also substitute your own lexer. A lexer is an object with a ``next()``\nmethod that returns either the next token in sequence, or ``None`` if the token\nstream has been exhausted.\n\nWhy do we have the boxes?\n-------------------------\n\nIn RPython, like other statically typed languages, a variable must have a\nspecific type, we take advantage of polymorphism to keep values in a box so\nthat everything is statically typed. You can write whatever boxes you need for\nyour project.\n\nIf you don't intend to use your parser from RPython, and just want a cool pure\nPython parser you can ignore all the box stuff and just return whatever you\nlike from each production method.\n\nError handling\n--------------\n\nBy default, when a parsing error is encountered, an ``rply.ParsingError`` is\nraised, it has a method ``getsourcepos()``, which returns an\n``rply.token.SourcePosition`` object.\n\nYou may also provide an error handler, which, at the moment, must raise an\nexception. It receives the ``Token`` object that the parser errored on.\n\n.. code:: python\n\n pg = ParserGenerator(...)\n\n @pg.error\n def error_handler(token):\n raise ValueError(\"Ran into a %s where it wasn't expected\" % token.gettokentype())\n\nPython compatibility\n--------------------\n\nRPly is tested and known to work under Python 2.7, 3.4+, and PyPy. It is\nalso valid RPython for PyPy checkouts from ``6c642ae7a0ea`` onwards.\n\nLinks\n-----\n\n* `Source code and issue tracker <https://github.com/alex/rply/>`_\n* `PyPI releases <https://pypi.python.org/pypi/rply>`_\n* `Talk at PyCon US 2013: So you want to write an interpreter? <http://pyvideo.org/video/1694/so-you-want-to-write-an-interpreter>`_\n\n.. _`online`: https://rply.readthedocs.io/\n\n\n",
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