Regular-Expresso Changeset

Changeset - f03565ba6137

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Laman - 10 months ago 2024-07-02 23:16:28

find_equivalent_states implemented with Hopcroft's n log n algorithm

3 files changed with 111 insertions and 54 deletions:

regexp.py

src/main.rs

src/regexp.rs

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regexp.py

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@@ @@ -225,277 +225,302 @@ class Regexp: @@
 			alphabet.add(c)
 			key = (-1, c)
 			if key not in rules:
 				rules[key] = set()
 			rules[key].add(i)
 		for (i, j) in r.list_neighbours():
 			c = pattern[j]
 			alphabet.add(c)
 			key = (i, c)
 			if key not in rules:
 				rules[key] = set()
 			rules[key].add(j)
 		end_states = set(r.list_last())
 		if r.is_skippable:
 			end_states.add(-1)
 		self.rules = rules
 		self.end_states = end_states
 		self.alphabet = alphabet
 	def match(self, s):
 		current = {-1}
 		for c in s:
 			new_state = set()
 			for st in current:
 				key = (st, c)
 				if key in self.rules:
 					new_state.update(self.rules[key])
 			current = new_state
 		return any(st in self.end_states for st in current)
 	def determinize(self):
 		alphabet_index = {c: i for (i, c) in enumerate(sorted(self.alphabet))}
 		n = len(alphabet_index)
 		compact_rules = [-1] * n
 		end_states = {0} if -1 in self.end_states else set()
 		index = {(-1,): 0}
 		stack = [(-1,)]
 		while stack:
 			multistate = stack.pop()
 			new_rules = dict()
 			for ((st, c), target) in filter(lambda item: item[0][0] in multistate, self.rules.items()):
 				if c not in new_rules:
 					new_rules[c] = set()
 				new_rules[c].update(target)
 			for (c, target_set) in new_rules.items():
 				target_tup = tuple(sorted(target_set))
 				if target_tup not in index:
 					new_target = len(index)
 					index[target_tup] = new_target
 					compact_rules.extend([-1] * n)
 					stack.append(target_tup)
 				compact_rules[index[multistate]*n + alphabet_index[c]] = index[target_tup]
 				if any(st in self.end_states for st in target_set):
 					end_states.add(index[target_tup])
 		fail = len(index)
 		compact_rules = [(st if st >= 0 else fail) for st in compact_rules]
 		compact_rules.extend([fail] * n)
 		return (compact_rules, end_states, alphabet_index)
 class RegexpDFA:
 	def __init__(self, rules, end_states, alphabet_index):
 		self.rules = rules or [1, 1]
 		self.end_states = end_states
 		self.alphabet_index = alphabet_index or {"": 0}
 	@classmethod
 	def create(cls, pattern):
 		r = Regexp(pattern)
 		(rules, end_states, alphabet_index) = r.determinize()
 		return cls(rules, end_states, alphabet_index)
 	def match(self, s):
 		st = 0
 		n = len(self.alphabet_index)
 		for c in s:
 			if c not in self.alphabet_index:
 				return False
 			key = (st*n + self.alphabet_index[c])
 			st = self.rules[key]
 		return st in self.end_states
 	def reduce(self):
 		equivalents = self._find_equivalent_states()
 		(rules, end_states) = self._collapse_states(equivalents)
 		partition = self._find_equivalent_states()
 		(rules, end_states) = self._collapse_states(partition)
 		return RegexpDFA(rules, end_states, self.alphabet_index)
 	def normalize(self):
 		n = len(self.alphabet_index)
 		index = {0: 0}
 		queue = deque([0])
 		rules = []
 		while queue:
 			si = queue.popleft()
 			row = self.rules[si*n:(si+1)*n]
 			for sj in row:
 				if sj not in index:
 					index[sj] = len(index)
 					queue.append(sj)
 			rules.extend(index[sj] for sj in row)
 		end_states = {index[si] for si in self.end_states if si in index}
 		return RegexpDFA(rules, end_states, self.alphabet_index)
 	def find_distinguishing_string(self, r):
 		if self.rules == r.rules and self.end_states == r.end_states:
 			return None
 		r1 = self._expand_alphabet(r.alphabet_index)
 		r2 = r._expand_alphabet(self.alphabet_index)
 		product = r1._build_product_automaton(r2)
 		n = len(product.alphabet_index)
 		reverse_alphabet_index = {v: k for (k, v) in product.alphabet_index.items()}
 		queue = deque([(0, "")])
 		visited = {0}
 		while queue:
 			(state, acc) = queue.popleft()
 			if state in product.end_states:
 				return acc
 			for (i, target) in enumerate(product.rules[state*n:(state+1)*n]):
 				if target not in visited:
 					queue.append((target, acc+reverse_alphabet_index[i]))
 					visited.add(target)
 		assert False
 	def _find_equivalent_states(self):
 		n = len(self.alphabet_index)
 		state_list = list(range(len(self.rules) // n))
 		equivalents = {(s1, s2) for (i, s1) in enumerate(state_list) for s2 in state_list[i+1:] if (s1 in self.end_states) == (s2 in self.end_states)}
 		m = len(self.rules) // n
 		inverse_rules = [set() for i in range(m*n)]
 		for i in range(m):
 			for j in range(n):
 				target = self.rules[i*n + j]
 				inverse_rules[target*n + j].add(i)
 		set_bag = [self.end_states, set(range(m))-self.end_states]
 		res = {0, 1}
 		work = {0, 1}
 		while work:
 			key = work.pop()
 			target_set = set_bag[key]
 			for j in range(n):
 				source_set = set(itertools.chain.from_iterable(inverse_rules[t*n + j] for t in target_set))
 				for k in res.copy():
 					part = set_bag[k]
 					intersection = part & source_set
 					diff = part - source_set
 					if not intersection or not diff:
 						continue
 					res.remove(k)
 					ki = len(set_bag)
 					set_bag.append(intersection)
 					res.add(ki)
 					kd = len(set_bag)
 					set_bag.append(diff)
 					res.add(kd)
 					if k in work:
 						work.remove(k)
 						work.add(ki)
 						work.add(kd)
 					elif len(intersection) < len(diff):
 						work.add(ki)
 					else:
 						work.add(kd)
 		ctrl = True
 		while ctrl:
 			ctrl = False
 			for (s1, s2) in equivalents.copy():
 				for ci in range(n):
 					t1 = self.rules[s1*n + ci]
 					t2 = self.rules[s2*n + ci]
 					key = (min(t1, t2), max(t1, t2))
 					if t1 != t2 and key not in equivalents:
 						equivalents.remove((s1, s2))
 						ctrl = True
 						break
 		return equivalents
 		return [set_bag[k] for k in res]
-	def _collapse_states(self, equivalents):
+	def _collapse_states(self, partition):
 		n = len(self.alphabet_index)
 		rules = []
 		eq_mapping = dict()
 		for (s1, s2) in equivalents:
 			eq_mapping[s2] = min(s1, eq_mapping.get(s2, math.inf))
 		for eq_set in partition:
 			states = sorted(eq_set)
 			for st in states:
 				eq_mapping[st] = states[0]
 		discard_mapping = dict()
 		discard_count = 0
 		for i in range(0, len(self.rules), n):
 			si = i//n
-			if si in eq_mapping:
+			if eq_mapping[si] != si:
 				discard_count += 1
 				continue
 			discard_mapping[si] = si - discard_count
-			rules.extend(map(lambda st: eq_mapping.get(st, st), self.rules[i:i+n]))
+			rules.extend(map(lambda st: eq_mapping[st], self.rules[i:i+n]))
 		rules = [discard_mapping[st] for st in rules]
-		end_states = {discard_mapping[eq_mapping.get(st, st)] for st in self.end_states}
+		end_states = {discard_mapping[eq_mapping[st]] for st in self.end_states}
 		return (rules, end_states)
 	def _expand_alphabet(self, alphabet_index):
 		if alphabet_index == self.alphabet_index:
 			return self
 		n1 = len(self.alphabet_index)
 		m = len(self.rules) // n1
 		combined_alphabet = set(self.alphabet_index.keys()) | set(alphabet_index.keys())
 		combined_index = {c: i for (i, c) in enumerate(sorted(combined_alphabet))}
 		conversion_index = {combined_index[k]: v for (k, v) in self.alphabet_index.items()}
 		n2 = len(combined_alphabet)
 		rules = [
 			self.rules[i*n1 + conversion_index[j]]
 			if j in conversion_index else m
 			for i in range(m) for j in range(n2)
+		]
 		rules.extend([m]*n2)
 		return RegexpDFA(rules, self.end_states, combined_index).reduce().normalize()
 	def _build_product_automaton(self, r):
 		n = len(self.alphabet_index)
 		m = len(r.rules) // n
 		k = len(self.rules) // n
 		rules = []
 		end_states = set()
 		for s1 in range(k):
 			row1 = self.rules[s1*n:(s1+1)*n]
 			for s2 in range(m):
 				row2 = r.rules[s2*n:(s2+1)*n]
 				rules.extend([x*m + y for (x, y) in zip(row1, row2)])
 				if (s1 in self.end_states) != (s2 in r.end_states):
 					end_states.add(s1*m + s2)
 		return RegexpDFA(rules, end_states, self.alphabet_index).reduce().normalize()
 def test():
 	tests = ["", "a", "ab", "aabb", "abab", "abcd", "abcbcdbcd"]
-	for pattern in ["a(b|c)", "a*b*", "(ab)*", "a((bc)*d)*", "(a|b)*a(a|b)(a|b)(a|b)", "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"]:
+	for pattern in ["a(b|c)", "a*b*", "(ab)*", "a((bc)*d)*", "(a|b)*a(a|b)(a|b)(a|b)", "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"]:
 		print("#", pattern)
 		try:
 			r = RegexpDFA.create(pattern).reduce().normalize()
 		except ParsingError as e:
 			print("Failed to parse the regexp:")
 			print(e)
 			continue
 		for t in tests:
 			print(t, r.match(t))
 		print()
 if __name__ == "__main__":
 	parser = argparse.ArgumentParser()
 	subparsers = parser.add_subparsers()
 	test_parser = subparsers.add_parser("test")
 	test_parser.set_defaults(name="test")
 	match_parser = subparsers.add_parser("match")
 	match_parser.add_argument("pattern")
 	match_parser.add_argument("string")
 	match_parser.set_defaults(name="match")
 	compare_parser = subparsers.add_parser("compare")
 	compare_parser.add_argument("pattern1")
 	compare_parser.add_argument("pattern2")
 	compare_parser.set_defaults(name="compare")
 	args = parser.parse_args()
 	if args.name == "test":
 		test()
 	elif args.name == "match":
 		try:
 			r = RegexpDFA.create(args.pattern).reduce().normalize()
 		except ParsingError as e:
 			print("Failed to parse the regexp:")
 			print(e)
 		print(r.match(args.string))
 	elif args.name == "compare":
 		r1 = RegexpDFA.create(args.pattern1).reduce().normalize()
 		r2 = RegexpDFA.create(args.pattern2).reduce().normalize()
 		print(r1.find_distinguishing_string(r2))
 	else:
 		parser.print_help()

src/main.rs

➞

Show inline comments

 use std::env;
 use regexp::Regexp;
 fn test() {
 	let tests = ["", "a", "ab", "aabb", "abab", "abcd", "abcbcdbcd"];
-	for pattern in ["a(b|c)", "a*b*", "(ab)*", "a((bc)*d)*", "(a|b)*a(a|b)(a|b)(a|b)", "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"] {
+	for pattern in ["a(b|c)", "a*b*", "(ab)*", "a((bc)*d)*", "(a|b)*a(a|b)(a|b)(a|b)", "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"] {
 		println!("# {pattern}");
 		let r = match Regexp::new(&pattern.to_string()) {
 			Ok(r1) => r1.determinize().reduce().normalize(),
 			Err(e) => {
 				println!("{e}");
 				continue;
+			}
 		};
 		for &t in tests.iter() {
 			println!("{t} {}", r.eval(t.to_string()));
+		}
 		println!();
+	}
+}
 fn main() {
 	let args: Vec<String> = env::args().collect();
 	match args[1].as_str() {
 		"test" => test(),
 		"match" => {
 			let r = match Regexp::new(&args[2].to_string()) {
 				Ok(r1) => r1.determinize().reduce().normalize(),
 				Err(e) => {
 					panic!("ERROR: {e}");
+				}
 			};
 			println!("{}", r.eval(args[3].to_string()));
 		},
 		"compare" => {
 			let r1 = match Regexp::new(&args[2].to_string()) {
 				Ok(r) => r.determinize().reduce().normalize(),
 				Err(e) => {
 					panic!("ERROR: {e}");
+				}
 			};
 			let r2 = match Regexp::new(&args[3].to_string()) {
 				Ok(r) => r.determinize().reduce().normalize(),
 				Err(e) => {
 					panic!("ERROR: {e}");
+				}
 			};
 			println!("{}", r1.find_distinguishing_string(&r2).unwrap_or("None".to_string()));
 		},
 		s => {
 			println!("An unknown command: \"{s}\". Use \"match\" or \"test\".")
+		}
+	}
+}

src/regexp.rs

➞

Show inline comments

@@ @@ -75,263 +75,295 @@ impl Regexp { @@
 			multistate = new_multistate;
+		}
 		return multistate.iter().any(|x| self.end_states.contains(x));
+	}
 	pub fn determinize(&self) -> RegexpDFA {
 		const FAIL: usize = usize::MAX;
 		let alphabet_index: HashMap<char, usize> = self.alphabet.iter().enumerate().map(|(i, c)| (*c, i)).collect();
 		let n = alphabet_index.len();
 		let mut compact_rules = vec![FAIL; n];
 		let mut end_states: HashSet<usize> = HashSet::new();
 		if self.end_states.contains(&START_NFA) {end_states.insert(START_DFA);}
 		// string hash -> single int DFA state
 		let mut index_new = HashMap::from([(START_NFA.to_string(), START_DFA)]);
 		// string hash -> HashSet NFA multistate
 		let mut index_multi = HashMap::from([(START_NFA.to_string(), HashSet::from([START_NFA]))]);
 		let mut stack = Vec::from([START_NFA.to_string()]);
 		while !stack.is_empty() {
 			let state_hash = stack.pop().unwrap();
 			let multistate = &index_multi[&state_hash];
 			let mut new_rules: HashMap<char, HashSet<usize>> = HashMap::new();
 			for key in self.rules.keys().filter(|(st, _c)| multistate.contains(st)) {
 				let (_st, c) = key;
 				if !new_rules.contains_key(c) {
 					new_rules.insert(*c, HashSet::new());
+				}
 				for target in &self.rules[key] {
 					new_rules.get_mut(c).unwrap().insert(*target);
+				}
+			}
 			for (c, target_set) in new_rules.into_iter() {
 				let target_hash = encode_set(&target_set);
 				let is_end = target_set.iter().any(|st| self.end_states.contains(st));
 				if !index_new.contains_key(&target_hash) {
 					let target_new = index_new.len();
 					index_new.insert(target_hash.clone(), target_new);
 					index_multi.insert(target_hash.clone(), target_set);
 					compact_rules.extend(iter::repeat(FAIL).take(n));
 					stack.push(target_hash.clone());
+				}
 				compact_rules[index_new[&state_hash]*n + alphabet_index[&c]] = index_new[&target_hash];
 				if is_end {
 					end_states.insert(index_new[&target_hash]);
+				}
+			}
+		}
 		let fail = index_new.len();
 		compact_rules = compact_rules.into_iter().map(|st| if st != FAIL {st} else {fail}).collect();
 		compact_rules.extend(iter::repeat(fail).take(n));
 		return RegexpDFA::new(compact_rules, end_states, alphabet_index);
+	}
+}
 #[derive(Clone)]
 pub struct RegexpDFA {
 	rules: Vec<usize>,
 	end_states: HashSet<usize>,
 	alphabet_index: HashMap<char, usize>
+}
 impl RegexpDFA {
 	pub fn new(rules: Vec<usize>, end_states: HashSet<usize>, alphabet_index: HashMap<char, usize>) -> RegexpDFA {
 		if rules.len() > 0 {
 			return RegexpDFA{rules, end_states, alphabet_index};
 		} else {
 			return RegexpDFA{
 				rules: vec![1, 1],
 				end_states,
 				alphabet_index: HashMap::from([('\0', 0)])
 			};
+		}
+	}
 	pub fn eval(&self, s: String) -> bool {
 		let n = self.alphabet_index.len();
 		let mut state = START_DFA;
 		for c in s.chars() {
 			if let Some(ci) = self.alphabet_index.get(&c) {
 				state = self.rules[state*n + ci];
 			} else {
 				return false;
+			}
+		}
 		return self.end_states.contains(&state);
+	}
 	pub fn reduce(&self) -> RegexpDFA {
 		let equivalents = self.find_equivalent_states();
 		return self.collapse_states(equivalents);
 		let partition = self.find_equivalent_states();
 		return self.collapse_states(partition);
+	}
 	pub fn normalize(&self) -> RegexpDFA {
 		let n = self.alphabet_index.len();
 		let m = self.rules.len()/n;
 		let fail = m;
 		let mut index: Vec<usize> = vec![fail;m];
 		index[0] = 0;
 		let mut queue = VecDeque::from([START_DFA]);
 		let mut rules = vec![];
 		let mut k = 1;
 		while !queue.is_empty() {
 			let si = queue.pop_front().unwrap();
 			let row = &self.rules[si*n..(si+1)*n];
 			for &sj in row {
 				if sj != fail && index[sj] == fail {
 					index[sj] = k;
 					k += 1;
 					queue.push_back(sj);
+				}
+			}
 			rules.extend(row.iter().map(|&st| index[st]));
+		}
 		let end_states = self.end_states.iter().map(|st| index[*st]).collect();
 		return RegexpDFA{rules, end_states, alphabet_index: self.alphabet_index.clone()};
+	}
 	pub fn find_distinguishing_string(&self, other: &RegexpDFA) -> Option<String> {
 		if self.rules == other.rules && self.end_states == other.end_states {
 			return None;
+		}
 		let r1 = self.expand_alphabet(&other.alphabet_index);
 		let r2 = other.expand_alphabet(&self.alphabet_index);
 		let product = r1.build_product_automaton(&r2);
 		let n = product.alphabet_index.len();
 		let reverse_alphabet_index: HashMap<usize, char> = HashMap::from_iter(product.alphabet_index.iter().map(|(&k, &v)| (v, k)));
 		let mut queue = VecDeque::from([(0, "".to_string())]);
 		let mut visited = HashSet::new();
 		while !queue.is_empty() {
 			let (state, acc) = queue.pop_front().unwrap();
 			if product.end_states.contains(&state) {
 				return Some(acc);
+			}
 			for (i, target) in product.rules[state*n..(state+1)*n].iter().enumerate() {
 				if !visited.contains(target) {
 					queue.push_back((*target, acc.clone()+&String::from(reverse_alphabet_index[&i])));
 					visited.insert(target);
+				}
+			}
+		}
 		panic!();
+	}
-	fn find_equivalent_states(&self) -> Vec<(usize, usize)> {
+	fn find_equivalent_states(&self) -> Vec<HashSet<usize>> {
 		let n = self.alphabet_index.len();
 		let state_vec: Vec<usize> = (0..self.rules.len()/n).collect();
 		let mut equivalents = HashSet::new();
 		state_vec.iter().enumerate().for_each(|(i, s1)| {
 			equivalents.extend(
 				state_vec[i+1..].iter()
 				.filter(|s2| !(self.end_states.contains(s1)^self.end_states.contains(s2)))
 				.map(|s2| (*s1, *s2))
 			);
 		});
 		let m = self.rules.len() / n;
 		let mut inverse_rules = vec![HashSet::<usize>::new();m*n];
 		let mut m = usize::MAX;
 		while equivalents.len() < m {
 			m = equivalents.len();
 			equivalents = equivalents.iter().filter(|(s1, s2)| {
 				!(0..n).any(|ci| {
 					let t1 = self.rules[s1*n + ci];
 					let t2 = self.rules[s2*n + ci];
 					let key = (t1.min(t2), t2.max(t1));
 					return t1 != t2 && !equivalents.contains(&key);
 				})
 			}).copied().collect();
 		for i in 0..m {
 			for j in 0..n {
 				let target = self.rules[i*n + j];
 				inverse_rules[target*n + j].insert(i);
+			}
+		}
 		return Vec::from_iter(equivalents.into_iter());
 		let mut set_bag = vec![
 			self.end_states.clone(),
 			HashSet::from_iter(0..m).difference(&self.end_states).copied().collect()
 		];
 		let mut res = HashSet::<usize>::from([0, 1]);
 		let mut work = HashSet::<usize>::from([0, 1]);
 		while !work.is_empty() {
 			let key = *work.iter().next().unwrap();
 			work.remove(&key);
 			let target_set = set_bag[key].clone();
 			for j in 0..n {
 				let source_set = HashSet::<usize>::from_iter(target_set.iter().flat_map(|&t| inverse_rules[t*n+j].iter()).copied());
 				for k in res.clone().into_iter() {
 					let part = &set_bag[k];
 					let intersection = part.intersection(&source_set).copied().collect::<HashSet<usize>>();
 					let diff = part.difference(&source_set).copied().collect::<HashSet<usize>>();
 					if intersection.is_empty() || diff.is_empty() {
 						continue;
+					}
 					res.remove(&k);
 					let ki = set_bag.len();
 					set_bag.push(intersection);
 					res.insert(ki);
 					let kd = set_bag.len();
 					set_bag.push(diff);
 					res.insert(kd);
 					if work.contains(&k) {
 						work.remove(&k);
 						work.insert(ki);
 						work.insert(kd);
 					} else if set_bag[ki].len() < set_bag[kd].len() {
 						work.insert(ki);
 					} else {
 						work.insert(kd);
+					}
+				}
+			}
+		}
 		return Vec::from_iter(res.into_iter().map(|k| std::mem::take(&mut set_bag[k])));
+	}
-	fn collapse_states(&self, equivalents: Vec<(usize, usize)>) -> RegexpDFA {
+	fn collapse_states(&self, partition: Vec<HashSet<usize>>) -> RegexpDFA {
 		let n = self.alphabet_index.len();
 		let m = self.rules.len()/n;
-		let mut rules = Vec::new();
+		let mut rules = vec![];
 		let mut eq_mapping: Vec<usize> = ((0..m)).collect();
 		for (s1, s2) in equivalents.into_iter() {
 			eq_mapping[s2] = eq_mapping[s2].min(s1);
 		for eq_set in partition.into_iter() {
 			let mut eq_vec = Vec::from_iter(eq_set.into_iter());
 			eq_vec.sort();
 			let label = eq_vec[0];
 			for st in eq_vec.into_iter() {
 				eq_mapping[st] = label;
+			}
+		}
 		let mut discard_mapping: Vec<usize> = ((0..m)).collect();
 		let mut discard_count = 0;
 		for si in 0..m {
 			if eq_mapping[si] != si {
 				discard_count += 1;
 				continue;
+			}
 			discard_mapping[si] = si-discard_count;
 			rules.extend(self.rules[si*n..(si+1)*n].iter().map(|&st| eq_mapping[st]));
+		}
 		rules = rules.into_iter().map(|st| discard_mapping[st]).collect();
 		let end_states = self.end_states.iter().map(|st| discard_mapping[eq_mapping[*st]]).collect();
 		return RegexpDFA{rules, end_states, alphabet_index: self.alphabet_index.clone()};
+	}
 	fn expand_alphabet(&self, alphabet_index: &HashMap<char, usize>) -> RegexpDFA {
 		if *alphabet_index == self.alphabet_index {
 			return self.clone();
+		}
 		let n1 = self.alphabet_index.len();
 		let m = self.rules.len() / n1;
 		let combined_alphabet: HashSet<char> = HashSet::from_iter(self.alphabet_index.keys().chain(alphabet_index.keys()).copied());
 		let mut combined_vec = Vec::from_iter(combined_alphabet.into_iter());
 		combined_vec.sort();
 		let combined_index = HashMap::from_iter(combined_vec.iter().enumerate().map(|(i, c)| (*c, i)));
 		let conversion_index: HashMap<usize, usize> = HashMap::from_iter(self.alphabet_index.iter().map(|(k, v)| (combined_index[k], *v)));
 		let n2 = combined_vec.len();
 		let rules: Vec<usize> = (0..m*n2).map(
 			|i| {
 				let (j, k) = (i/n2, i%n2);
 				return if conversion_index.contains_key(&k) {
 					self.rules[j*n1 + conversion_index[&k]]
 				} else {m};
+			}
 		).chain(std::iter::repeat(m).take(n2)).collect();
 		return RegexpDFA{rules, end_states: self.end_states.clone(), alphabet_index: combined_index}.reduce().normalize();
+	}
 	fn build_product_automaton(&self, other: &RegexpDFA) -> RegexpDFA {
 		let n = self.alphabet_index.len();
 		let m = other.rules.len() / n;
 		let k = self.rules.len() / n;
 		let mut rules = vec![];
 		let mut end_states = HashSet::new();
 		for s1 in 0..k {
 			let row1 = &self.rules[s1*n..(s1+1)*n];
 			for s2 in 0..m {
 				let row2 = &other.rules[s2*n..(s2+1)*n];
 				rules.extend(row1.iter().zip(row2.iter()).map(|(x, y)| x*m + y));
 				if (self.end_states.contains(&s1)) ^ (other.end_states.contains(&s2)) {
 					end_states.insert(s1*m + s2);
+				}
+			}
+		}
 		return RegexpDFA{rules, end_states, alphabet_index: self.alphabet_index.clone()}.reduce().normalize();
+	}
+}

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