Comments (10)
(and regarding your last question, self._test_compare
only tests that PythonRegex
has the same behavior as re
. It does not assume the word is accepted or not. In your example, both modules return False, which is good)
from pyformlang.
I have found some new hard cases! It looks like the escaping of a dot with backslashes in front does not behave correctly:
from pyformlang.regular_expression import PythonRegex
PythonRegex(r"\.").accepts(["a"]) # Returns False
PythonRegex(r"\.").accepts(["."]) # Returns True
PythonRegex(r"\\.").accepts(["\\a"]) # Returns False, should be True
PythonRegex(r"\\.").accepts(["\\."]) # Returns False, should be True
PythonRegex(r"\\\.").accepts(["\\a"]) # Returns False
PythonRegex(r"\\\.").accepts(["\\."]) # Returns False, should be True
from pyformlang.
Thank you for your feedback. There were three different issues:
"-"
denotes a range, but if the range contains escaped characters (like"|"
), we need to really escape them when unfolding the range."["
and"]"
were not able to be escaped inside a"[...]"
- (not mentioned here but appeared)
r"a[ab\\]"
had a weird behavior. In some cases, we need to ignore the escaping of the last "]" (I am not quite sure what the rule is; if there is an odd number of"\"
, there
module in Python raises an error).
Thank you again for your help in finding bug :) I added your examples to the tests, and they should be working now. A new version was pushed on Pypi.
from pyformlang.
Thanks for the quick fix! However, I think ranges where the ending character is escaped still do not work correctly. r"[{-}]"
correctly accepts {
, |
and }
. However, r"[{-\}]"
only accepts {
and }
, but not |
. Escaping the first {
does not change the behavior. Similar for the brackets: r"[\[-\]]"
only accepts [
and ]
, but not \
.
(Also, it looks like you added the test self._test_compare(r"[{-}]", "-")
, but r"[{-}]"
should, and does not, accept -
and should, and does, accept |
. Shouldn't the automated test fail?)
from pyformlang.
Thanks again.
Ultimately, I had to work harder to understand what Python is actually doing and how escaping works (https://docs.python.org/3/reference/lexical_analysis.html#escape-sequences). I am not quite sure I mimic exactly the behavior of Python re in all edge cases, but it should be closer now.
I discovered weird things. For example, the three following regexes seem to have the same behavior:
r = re.compile("\\x10")
r = re.compile("\x10")
r = re.compile(r"\x10")
To recognize the string \x10 (not hexadecimal equivalent), we have to escape twice:
r = re.compile("\\\\x10")
At this point, I am not sure anybody is writing such regex...
Anyway, it should work better now. A new version was pushed. Tell me if you find other hard cases!
from pyformlang.
Thanks! It looks like it works correctly now.
from pyformlang.
Thank you again! I quickly found the bug and corrected it.
from pyformlang.
Thanks for quick response, but it doesn't seem to be fixed? When I install version 1.0.7, I get the same results in my example as before?
from pyformlang.
In your examples, you have to remove the square brackets. Otherwise, Pyformlang understands that "\\a" is a single symbol/letter (because Pyformlang is more general in a way than Python re).
from pyformlang.
Ah yes, I forgot about that part. Thanks, it works now! Then my examples were also incorrect as the last one did already return True
, but 'luckily' the middle two were indeed wrong...
from pyformlang.
Related Issues (10)
- Standard regular expression HOT 1
- pyformlang.regular_expression.regex_objects.MisformedRegexError: Wrong parenthesis regex Regex HOT 1
- Is there algorith to convert epsNFA to NFA (remove epsilon transitions)? HOT 7
- Trouble with epsilon in CFG HOT 3
- Trouble with Regex HOT 1
- Bug with CNF HOT 1
- Bug with to_normal_form() function HOT 2
- Question: PDA final state or empty stack? HOT 2
- AttributeError: module 'pyformlang' has no attribute 'regular_expression' HOT 1
Recommend Projects
-
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
-
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
-
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
-
TensorFlow
An Open Source Machine Learning Framework for Everyone
-
Django
The Web framework for perfectionists with deadlines.
-
Laravel
A PHP framework for web artisans
-
D3
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
-
Recommend Topics
-
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
-
web
Some thing interesting about web. New door for the world.
-
server
A server is a program made to process requests and deliver data to clients.
-
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
-
Visualization
Some thing interesting about visualization, use data art
-
Game
Some thing interesting about game, make everyone happy.
Recommend Org
-
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
-
Microsoft
Open source projects and samples from Microsoft.
-
Google
Google ❤️ Open Source for everyone.
-
Alibaba
Alibaba Open Source for everyone
-
D3
Data-Driven Documents codes.
-
Tencent
China tencent open source team.
from pyformlang.