diff --git a/regexp.py b/regexp.py
new file mode 100644
--- /dev/null
+++ b/regexp.py
@@ -0,0 +1,136 @@
+from abc import abstractmethod
+
+
+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
+
+	def list_last(self):
+		yield self.position
+
+	def list_neighbours(self):
+		yield from []
+
+	def __str__(self):
+		return self.value
+
+
+class Asterisk(Token):
+	is_skippable = True
+
+	def __init__(self, content: Token):
+		self.content = content
+
+	def list_first(self):
+		yield from self.content.list_first()
+
+	def list_last(self):
+		yield from self.content.list_last()
+
+	def list_neighbours(self):
+		yield from self.content.list_neighbours()
+		for x in self.list_last():
+			for y in self.list_first():
+				yield (x, y)
+
+	def __str__(self):
+		return str(self.content) + "*"
+
+
+class Chain(Token):
+	def __init__(self, content: list):
+		self.content = content
+
+	def list_first(self):
+		for token in self.content:
+			yield from token.list_first()
+			if not token.is_skippable:
+				break
+
+	def list_last(self):
+		for token in reversed(self.content):
+			yield from token.list_last()
+			if not token.is_skippable:
+				break
+
+	def list_neighbours(self):
+		previous = []
+		for token in self.content:
+			for t in previous:
+				for x in t.list_last():
+					for y in token.list_first():
+						yield (x, y)
+			yield from token.list_neighbours()
+
+			if token.is_skippable:
+				previous.append(token)
+			else:
+				previous = [token]
+
+	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
+
+
+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 == "*":
+			token = res.pop()
+			res.append(Asterisk(token))
+			i += 1
+		else:
+			res.append(Symbol(i+offset, c))
+			i += 1
+
+	return Chain(res)
+
+
+if __name__ == "__main__":
+	for pattern in ["a*b*", "(ab)*", "a((bc)*d)*"]:
+		print("#", pattern)
+		p = parse(pattern)
+		print(p, list(p.list_first()), list(p.list_last()))
+		print(list(p.list_neighbours()))
+		print()