lookahead.py

class Parser(self):
	def advance(self):
			""" Advance the tokens in use
			"""
			self.current_token, self.next_token = self.next_token, next(self.tokens, None)


	def accept(self, expected, raise_err = True):
		""" Helper function to check if the next token is what we expect

		Params:
			expected (str) - Either the exact token we expect e.g. "SELECT" or the token type we expect e.g. "name"
			raise_err (bool) - Whether or not to raise an error and halt program

		Returns:
			(bool) - Whether the next token is what's expected
		"""
		if(self.next_token["token"] == expected or self.next_token["token_type"] == expected):
			print(f"{self.next_token} == ({expected})")
			self.advance()
			if(self.next_token is None):
				if(self.current_token["token_type"] == "terminal"):
					print("No more tokens. Printing parse tree.... \n")
				else:
					raise ParsingErrorException(f"Semi-colon (;) expected at the end of the query")
			return True
		else:
			if(raise_err):
				raise ParsingErrorException(f"Unexpected token {self.next_token}. Expected {expected}. Please refer to the grammar {bnf}")
			return False