Regular-Expresso Changeset

Changeset - 7e640b0cffa7

Parent rev.

Child rev.

[Not reviewed]

default

0 6 0

Laman - 10 months ago 2024-06-18 16:21:22

handling unparsable patterns

6 files changed with 109 insertions and 27 deletions:

regexp.py

src/lib.rs

src/main.rs

src/regexp.rs

src/regexp/token.rs

tests/test_regexp.rs

0 comments (0 inline, 0 general)

regexp.py

➞

Show inline comments

 from abc import abstractmethod
 class ParsingError(Exception):
 	pass
 class Token:
 	is_skippable = False
 	@abstractmethod
 	def list_first(self):
 		pass
 	@abstractmethod
 	def list_last(self):
 		pass
 	@abstractmethod
 	def list_neighbours(self):
 		pass
 class Symbol(Token):
 	def __init__(self, position, value):
 		self.position = position
 		self.value = value
 	def list_first(self):
 		yield self.position
@@ @@ -90,70 +94,78 @@ class Chain(Token): @@
 			if token.is_skippable:
 				previous.append(token)
 			else:
 				previous = [token]
 	@property
 	def is_skippable(self):
 		return all(x.is_skippable for x in self.content)
 	def __str__(self):
 		return "(" + "".join(str(x) for x in self.content) + ")"
 def find_closing_parenthesis(pattern, k):
 	counter = 0
 	for (i, c) in enumerate(pattern[k:]):
 		if c == "(":
 			counter += 1
 		elif c == ")":
 			counter -= 1
 		if counter == 0:
 			return k+i
-	return None
+	raise ParsingError(f'A closing parenthesis not found. Pattern: "{pattern}", position: {k}')
 def parse(pattern, offset=0):
 	res = []
 	i = 0
 	while i < len(pattern):
 		c = pattern[i]
 		if c == "(":
 			j = find_closing_parenthesis(pattern, i)
 			inner_content = parse(pattern[i+1:j], offset+i+1)
 			res.append(inner_content)
 			i = j+1
 		elif c == "*":
 			try:
 			token = res.pop()
 			except IndexError as e:
 				raise ParsingError(f'The asterisk operator is missing an argument. Pattern: "{pattern}", position {i}')
 			res.append(Asterisk(token))
 			i += 1
 		elif c == "+":
 			try:
 			token = res.pop()
 			except IndexError as e:
 				raise ParsingError(f'The plus operator is missing an argument. Pattern: "{pattern}", position {i}')
 			res.append(Plus(token))
 			i += 1
 		elif c == ")":
 			raise ParsingError(f'An opening parenthesis not found. Pattern: "{pattern}", position: {i}')
 		else:
 			res.append(Symbol(i+offset, c))
 			i += 1
 	return Chain(res)
 class Regexp:
 	def __init__(self, pattern):
 		(self.rules, self.end_states) = self._parse(pattern)
 	def _parse(self, s):
 		r = parse(s)
 		rules = dict()
 		for i in r.list_first():
 			c = s[i]
 			key = (-1, c)
 			if key not in rules:
 				rules[key] = set()
 			rules[key].add(i)
 		for (i, j) in r.list_neighbours():
 			c = s[j]
@@ @@ -207,30 +219,35 @@ class Regexp: @@
 		return (rules, end_states)
 class RegexpDFA:
 	def __init__(self, pattern):
 		r = Regexp(pattern)
 		(self.rules, self.end_states) = r.determinize()
 	def match(self, s):
 		st = (-1,)
 		for c in s:
 			key = (st, c)
 			if key in self.rules:
 				st = self.rules[key]
 			else:
 				return False
 		return st in self.end_states
 if __name__ == "__main__":
 	tests = ["", "a", "ab", "aabb", "abab", "abcd", "abcbcdbcd"]
-	for pattern in ["a*b*", "a+b+", "(ab)*", "(ab)+", "a((bc)*d)*"]:
+	for pattern in ["*", "((a)", "a)"]:
 		print("#", pattern)
 		try:
 		r = RegexpDFA(pattern)
 		except ParsingError as e:
 			print("Failed to parse the regexp:")
 			print(e)
 			continue
 		for t in tests:
 			print(t, r.match(t))
 		print()

src/lib.rs

➞

Show inline comments

 mod regexp;
 pub use regexp::Regexp;
+pub use regexp::{Regexp, ParsingError};

src/main.rs

➞

Show inline comments

 use regexp::Regexp;
 fn main() {
 	let tests = ["", "a", "ab", "aabb", "abab", "abcd", "abcbcdbcd"];
-	for pattern in ["a*b*", "a+b+", "(ab)*", "(ab)+", "a((bc)*d)*"] {
+	for pattern in ["*", "((a)", "a)", "+a"] {
 		println!("# {pattern}");
 		let r = Regexp::new(&pattern.to_string()).determinize();
 		let r = match Regexp::new(&pattern.to_string()) {
 			Ok(r1) => r1.determinize(),
 			Err(e) => {
 				println!("{e}");
 				continue;
+			}
 		};
 		for &t in tests.iter() {
 			println!("{t} {}", r.eval(t.to_string()));
+		}
 		println!();
+	}
+}

src/regexp.rs

➞

Show inline comments

 use std::collections::{HashMap, HashSet};
 mod token;
 pub use token::ParsingError;
 use token::{Token, parse};
 const START: usize = usize::MAX;
 fn encode_set(set: &HashSet<usize>) -> u64 {
 	let mut res = 0;
 	for x in set.iter() {
 		res ^= 1<<x;
+	}
 	return res;
+}
 fn decode_set(x: u64) ->HashSet<usize> {
 	if x == START as u64 {return HashSet::from([START]);}
 	let mut x = x;
 	let mut res: HashSet<usize> = HashSet::new();
 	while x > 0 {
 		let y = x.trailing_zeros();
 		res.insert(y as usize);
 		x ^= 1 << y;
+	}
 	return res;
+}
 #[derive(Debug)]
 pub struct Regexp {
 	rules: HashMap<(usize, char), HashSet<usize>>,
 	end_states: HashSet<usize>
+}
 impl Regexp {
 	pub fn new(pattern: &String) -> Regexp {
 		let r = parse(pattern, 0);
 	pub fn new(pattern: &String) -> Result<Regexp, ParsingError> {
 		let r = parse(pattern, 0)?;
 		let pattern_chars = Vec::from_iter(pattern.chars());
 		let mut rules: HashMap<(usize, char), HashSet<usize>> = HashMap::new();
 		for i in r.list_first() {
 			let c = pattern_chars[i];
 			let key = (START, c);
 			match rules.get_mut(&key) {
 				Some(set) => {set.insert(i);},
 				None => {rules.insert(key, HashSet::from([i]));}
 			};
+		}
 		for (i, j) in r.list_neighbours() {
 			let c = pattern_chars[j];
 			let key = (i, c);
 			match rules.get_mut(&key) {
 				Some(set) => {set.insert(j);},
 				None => {rules.insert(key, HashSet::from([j]));}
 			};
+		}
 		let mut end_states = HashSet::from_iter(r.list_last().into_iter());
 		if r.is_skippable() {
 			end_states.insert(START);
+		}
 		return Regexp{rules, end_states};
+		return Ok(Regexp{rules, end_states});
+	}
 	pub fn eval(&self, s: String) -> bool {
 		let mut multistate = HashSet::from([START]);
 		for c in s.chars() {
 			let mut new_multistate = HashSet::new();
 			for state in multistate {
 				if let Some(x) = self.rules.get(&(state, c)) {
 					new_multistate = new_multistate.union(&x).map(|&y| y).collect();
 				} else if let Some(x) = self.rules.get(&(state, '.')) {
 					new_multistate = new_multistate.union(&x).map(|&y| y).collect();
+				}
+			}
 			multistate = new_multistate;
+		}
 		return multistate.iter().any(|x| self.end_states.contains(x));
+	}
 	pub fn determinize(&self) -> RegexpDFA {
 		let mut rules: HashMap<(u64, char), u64> = HashMap::new();
 		let mut end_states: HashSet<u64> = HashSet::new();

src/regexp/token.rs

➞

Show inline comments

 use std::fmt;
 #[derive(Debug, Clone)]
 pub enum ParsingError {
 	Asterisk {s: String, pos: usize},
 	Plus {s: String, pos: usize},
 	OpeningParenthesis {s: String, pos: usize},
 	ClosingParenthesis {s: String, pos: usize}
+}
 impl fmt::Display for ParsingError {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		match self {
 			ParsingError::Asterisk {s, pos} => {
 				write!(f, "The asterisk operator is missing an argument. Pattern \"{s}\", position {pos}")
 			},
 			ParsingError::Plus {s, pos} => {
 				write!(f, "The plus operator is missing an argument. Pattern \"{s}\", position {pos}")
 			},
 			ParsingError::OpeningParenthesis {s, pos} => {
 				write!(f, "An opening parenthesis not found. Pattern \"{s}\", position {pos}")
 			},
 			ParsingError::ClosingParenthesis {s, pos} => {
 				write!(f, "An closing parenthesis not found. Pattern \"{s}\", position {pos}")
+			}
+		}
+	}
+}
 pub trait Token {
 	fn is_skippable(&self) -> bool {false}
 	fn list_first(&self) -> Vec<usize>;
 	fn list_last(&self) -> Vec<usize>;
 	fn list_neighbours(&self) -> Vec<(usize, usize)>;
+}
 pub struct Symbol {
 	position: usize,
 	value: char
+}
 pub struct Asterisk {
 	content: Box<dyn Token>
+}
 pub struct Plus {
 	content: Box<dyn Token>
+}
 pub struct Chain {
 	content: Vec<Box<dyn Token>>
+}
@@ @@ -123,66 +152,69 @@ impl Token for Chain { @@
 			if token.is_skippable() {
 				previous.push(token);
 			} else {
 				previous = vec![token];
+			}
+		}
 		return res;
+	}
+}
 fn find_closing_parenthesis(s: &String) -> Option<usize> {
 	let chars: Vec<char> = s.chars().collect();
 	let mut counter = 0;
 	for (i, c) in chars.iter().enumerate() {
 		if *c == '(' {counter += 1;}
 		else if *c == ')' {counter -= 1;}
 		if counter == 0 {return Some(i);}
+	}
 	return None;
+}
 pub fn parse(pattern: &String, offset: usize) -> Chain {
+pub fn parse(pattern: &String, offset: usize) -> Result<Chain, ParsingError> {
 	let chars: Vec<char> = pattern.chars().collect();
 	let mut res: Vec<Box<dyn Token>> = Vec::new();
 	let mut i = 0;
 	while i < pattern.len() {
 		let c = chars[i];
 		match c {
 			'(' => {
 				let j = find_closing_parenthesis(&pattern[i..].to_string()).unwrap() + i;
 				let inner_content = parse(&pattern[i+1..j].to_string(), offset+i+1);
 				let j = find_closing_parenthesis(&pattern[i..].to_string()).ok_or(ParsingError::ClosingParenthesis {s: pattern.clone(), pos: i})? + i;
 				let inner_content = parse(&pattern[i+1..j].to_string(), offset+i+1)?;
 				res.push(Box::new(inner_content));
 				i = j+1;
+			}
 			'*' => {
-				let token = res.pop().unwrap();
+				let token = res.pop().ok_or(ParsingError::Asterisk{s: pattern.clone(), pos: i})?;
 				res.push(Box::new(Asterisk{content: token}));
 				i += 1;
+			}
 			'+' => {
-				let token = res.pop().unwrap();
+				let token = res.pop().ok_or(ParsingError::Plus{s: pattern.clone(), pos: i})?;
 				res.push(Box::new(Plus{content: token}));
 				i += 1;
+			}
 			')' => {
 				return Err(ParsingError::OpeningParenthesis {s: pattern.clone(), pos: i});
+			}
 			c => {
 				res.push(Box::new(Symbol{position: i+offset, value: c}));
 				i += 1;
+			}
+		}
+	}
 	return Chain{content: res};
+	return Ok(Chain{content: res});
+}
 mod test {
 	use super::*;
 	#[test]
 	fn test_closing_parenthesis() {
 		let s = "()";
 		assert_eq!(find_closing_parenthesis(&s.to_string()), Some(1));
+	}
+}

tests/test_regexp.rs

➞

Show inline comments

 use regexp::Regexp;
 use regexp::ParsingError;
 #[test]
 fn test_eval_basic_nfa() {
 	let r = Regexp::new(&String::from("abc"));
+	let r = Regexp::new(&String::from("abc")).unwrap();
 	assert!(r.eval(String::from("abc")));
 	assert!(!r.eval(String::from("ab")));
 	assert!(!r.eval(String::from("abcd")));
+}
 #[test]
 fn test_eval_basic_dfa() {
 	let r = Regexp::new(&String::from("abc")).determinize();
+	let r = Regexp::new(&String::from("abc")).unwrap().determinize();
 	assert!(r.eval(String::from("abc")));
 	assert!(!r.eval(String::from("ab")));
 	assert!(!r.eval(String::from("abcd")));
+}
 #[test]
 fn test_eval_empty_nfa() {
 	assert!(Regexp::new(&String::from("a*")).eval(String::from("")));
 	assert!(Regexp::new(&String::from("")).eval(String::from("")));
 	assert!(!Regexp::new(&String::from("")).eval(String::from("a")));
 	assert!(!Regexp::new(&String::from("a")).eval(String::from("")));
 	assert!(Regexp::new(&String::from("a*")).unwrap().eval(String::from("")));
 	assert!(Regexp::new(&String::from("")).unwrap().eval(String::from("")));
 	assert!(!Regexp::new(&String::from("")).unwrap().eval(String::from("a")));
 	assert!(!Regexp::new(&String::from("a")).unwrap().eval(String::from("")));
+}
 #[test]
 fn test_eval_empty_dfa() {
 	assert!(Regexp::new(&String::from("a*")).determinize().eval(String::from("")));
 	assert!(Regexp::new(&String::from("")).determinize().eval(String::from("")));
 	assert!(!Regexp::new(&String::from("")).determinize().eval(String::from("a")));
 	assert!(Regexp::new(&String::from("a*")).unwrap().determinize().eval(String::from("")));
 	assert!(Regexp::new(&String::from("")).unwrap().determinize().eval(String::from("")));
 	assert!(!Regexp::new(&String::from("")).unwrap().determinize().eval(String::from("a")));
+}
 #[test]
 fn test_eval_asterisk_nfa() {
 	let r = Regexp::new(&String::from("a*b*"));
+	let r = Regexp::new(&String::from("a*b*")).unwrap();
 	assert!(r.eval(String::from("a")));
 	assert!(r.eval(String::from("ab")));
 	assert!(r.eval(String::from("aabb")));
 	assert!(!r.eval(String::from("abab")));
+}
 #[test]
 fn test_eval_asterisk_dfa() {
 	let r = Regexp::new(&String::from("a*b*")).determinize();
+	let r = Regexp::new(&String::from("a*b*")).unwrap().determinize();
 	assert!(r.eval(String::from("a")));
 	assert!(r.eval(String::from("ab")));
 	assert!(r.eval(String::from("aabb")));
 	assert!(!r.eval(String::from("abab")));
+}
 #[test]
 fn test_eval_plus_nfa() {
 	let r = Regexp::new(&String::from("(ab)+"));
+	let r = Regexp::new(&String::from("(ab)+")).unwrap();
 	assert!(!r.eval(String::from("a")));
 	assert!(r.eval(String::from("ab")));
 	assert!(r.eval(String::from("abab")));
 	assert!(!r.eval(String::from("aabb")));
+}
 #[test]
 fn test_eval_plus_dfa() {
 	let r = Regexp::new(&String::from("(ab)+")).determinize();
+	let r = Regexp::new(&String::from("(ab)+")).unwrap().determinize();
 	assert!(!r.eval(String::from("a")));
 	assert!(r.eval(String::from("ab")));
 	assert!(r.eval(String::from("abab")));
 	assert!(!r.eval(String::from("aabb")));
+}
 #[test]
 fn test_invalid_asterisk() {
 	let x = Regexp::new(&String::from("*"));
 	assert!(matches!(x, Err(ParsingError::Asterisk{s: _, pos: 0})));
+}
 #[test]
 fn test_invalid_plus() {
 	let x = Regexp::new(&String::from("+"));
 	assert!(matches!(x, Err(ParsingError::Plus{s: _, pos: 0})));
+}
 #[test]
 fn test_invalid_closing_parenthesis() {
 	let x = Regexp::new(&String::from("(a"));
 	assert!(matches!(x, Err(ParsingError::ClosingParenthesis{s: _, pos: 0})));
+}
 #[test]
 fn test_invalid_opening_parenthesis() {
 	let x = Regexp::new(&String::from("a)"));
 	assert!(matches!(x, Err(ParsingError::OpeningParenthesis{s: _, pos: 1})));
+}

0 comments (0 inline, 0 general)