"""Read (and write) a Recursive State Automaton from (and to) different sources."""
import logging
import pathlib
from typing import Union
from pyformlang.cfg import Epsilon, Variable, Production
from pyformlang.finite_automaton import Symbol
from pyformlang.finite_automaton.finite_automaton import to_symbol
from pyformlang.regular_expression import Regex
from pyformlang.rsa import Box, RecursiveAutomaton as RSA
__all__ = [
"rsa_from_text",
"rsa_to_text",
"rsa_from_txt",
"rsa_to_txt",
]
[docs]
def rsa_from_text(text: str, *, start_symbol: Symbol = Symbol("S")) -> RSA:
"""Create a Recursive State Automaton [1]_ from text.
Parameters
----------
text : str
The text with which the Recursive State Machine will be created.
start_symbol : Symbol
Start symbol of a Recursive State Machine.
Examples
--------
>>> from cfpq_data import *
>>> rsa = rsa_from_text("S -> a*")
>>> cfg_to_text(cfg_from_rsa(rsa))
'S -> \\nS -> a S'
Returns
-------
rsa : RSA
Recursive State Automaton.
References
----------
.. [1] Alur R., Etessami K., Yannakakis M. (2001) Analysis of Recursive State Machines.
In: Berry G., Comon H., Finkel A. (eds) Computer Aided Verification. CAV 2001.
Lecture Notes in Computer Science, vol 2102.
Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-44585-4_18
"""
productions = dict()
boxes = set()
labels = set()
for production in text.splitlines():
if " -> " not in production:
continue
head, body = production.split(" -> ")
labels.add(to_symbol(head))
if body == "":
body = Epsilon().to_text()
if head in productions:
productions[head] += " | " + body
else:
productions[head] = body
for head, body in productions.items():
boxes.add(Box(Regex(body).to_epsilon_nfa().minimize(), to_symbol(head)))
rsa = RSA(labels=labels, initial_label=start_symbol, boxes=boxes)
logging.info(f"Create {rsa=} from {text=}, {start_symbol=}")
return rsa
[docs]
def rsa_to_text(rsa: RSA) -> str:
"""Turns a Recursive State Automaton [1]_ into its text representation.
Parameters
----------
rsa : RSA
Recursive State Automaton.
Examples
--------
>>> from cfpq_data import *
>>> rsa = rsa_from_text("S -> a*")
>>> rsa_to_text(rsa)
'S -> (a)*'
Returns
-------
text : str
Recursive State Automaton text representation.
References
----------
.. [1] Alur R., Etessami K., Yannakakis M. (2001) Analysis of Recursive State Machines.
In: Berry G., Comon H., Finkel A. (eds) Computer Aided Verification. CAV 2001.
Lecture Notes in Computer Science, vol 2102.
Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-44585-4_18
"""
productions = []
for symbol in rsa.labels:
box = rsa.get_box(symbol)
productions.append(f"{box.label.value} -> {box.dfa.to_regex()}")
productions.sort(
key=lambda s: (s.split(" -> ")[0] != rsa.initial_label.value, s),
)
text = "\n".join(productions)
logging.info(f"Turn {rsa=} into {text=}")
return text
[docs]
def rsa_from_txt(
path: Union[pathlib.Path, str], *, start_symbol: Symbol = Symbol("S")
) -> RSA:
"""Create a Recursive State Automaton [1]_ from TXT file.
Parameters
----------
path : Union[Path, str]
The path to the TXT file with which the Recursive State Machine
will be created.
start_symbol : Symbol
Start symbol of a Recursive State Machine.
Examples
--------
>>> from cfpq_data import *
>>> rsa_1 = rsa_from_text("S -> a*")
>>> path = rsa_to_txt(rsa_1, "test.txt")
>>> rsa = rsa_from_txt(path)
>>> rsa_to_text(rsa)
'S -> (a)*'
Returns
-------
rsa : RSA
Recursive State Automaton.
References
----------
.. [1] Alur R., Etessami K., Yannakakis M. (2001) Analysis of Recursive State Machines.
In: Berry G., Comon H., Finkel A. (eds) Computer Aided Verification. CAV 2001.
Lecture Notes in Computer Science, vol 2102.
Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-44585-4_18
"""
with open(path, "r") as f:
productions = f.read()
rsa = rsa_from_text(productions, start_symbol=start_symbol)
logging.info(f"Create {rsa=} from {path=}, {start_symbol=}")
return rsa
[docs]
def rsa_to_txt(rsa: RSA, path: Union[pathlib.Path, str]) -> pathlib.Path:
"""Saves a Recursive State Automaton text representation into TXT file.
Parameters
----------
rsa : RSA
Recursive State Automaton.
path : Union[Path, str]
The path to the TXT file where Recursive State Machine
text representation will be saved.
Examples
--------
>>> from cfpq_data import *
>>> rsa = rsa_from_text("S -> (a S* b S*)*")
>>> path = rsa_to_txt(rsa, "test.txt")
Returns
-------
path : Path
The path to the TXT file where Recursive State Automaton
text representation will be saved.
References
----------
.. [1] Alur R., Etessami K., Yannakakis M. (2001) Analysis of Recursive State Machines.
In: Berry G., Comon H., Finkel A. (eds) Computer Aided Verification. CAV 2001.
Lecture Notes in Computer Science, vol 2102.
Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-44585-4_18
"""
with open(path, "w") as f:
f.write(rsa_to_text(rsa))
dest = pathlib.Path(path).resolve()
logging.info(f"Save {rsa=} to {dest=}")
return dest
