Interegular

regex intersection checker

A library to check a subset of python regexes for intersections. Based on greenery by @qntm. Adapted for lark-parser.

The primary difference with greenery library is that interegular is focused on speed and compatibility with python re syntax, whereas greenery has a way to reconstruct a regex from a FSM, which interegular lacks.

Interface

Function	Usage
compare_regexes(*regexes: str)	Takes a series of regexes as strings and returns a Generator of all intersections as (str, str)
parse_pattern(regex: str)	Parses a regex as string to a Pattern object
interegular.compare_patterns(*patterns: Pattern)	Takes a series of regexes as patterns and returns a Generator of all intersections as (Pattern, Pattern)
Pattern	A class representing a parsed regex (intermediate representation)
REFlags	A enum representing the flags a regex can have
FSM	A class representing a fully parsed regex. (Has many useful members)
Pattern.with_flags(added: REFlags, removed: REFlags)	A function to change the flags that are applied to a regex
Pattern.to_fsm() -> FSM	A function to create a FSM object from the Pattern
Comparator	A Class to compare a group of Patterns

What is supported?

Most normal python-regex syntax is support. But because of the backend that is used (final-state-machines), some things can not be implemented. This includes:

• Backwards references (\1, (?P=open))
• Conditional Matching ((?(1)a|b))
• Some cases of lookaheads/lookbacks (You gotta try out which work and which don't)
  • A word of warning: This is currently not correctly handled, and some things might parse, but not work correctly. I am currently working on this.

Some things are simply not implemented and will implemented in the future:

• Some flags (Progress: ims from aiLmsux)
• Some cases of lookaheads/lookbacks (You gotta try out which work and which don't)

TODO

• Docs
• More tests
• Checks that the syntax is correctly handled.