Fix this tokenizer keeping it as similar as possible class Tokenizer: def __init__(self, input_str): self.tokens = re.findall(r'\d+|(\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position]
Fix this tokenizer keeping it as similar as possible class Tokenizer: def __init__(self, input_str): self.tokens = re.findall(r'\d+|(\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position]
Below is one acceptable fix. The issue was that using a capturing group in the regex causes re.findall to return only the captured group instead of the full match. By replacing the capturing group with a non‐capturing group, we maintain all tokens (both numbers and operators) correctly. Here’s the updated code: ------------------------------------------------ import re class Tokenizer: def __init__(self, input_str): self.tokens = re.findall(r'\d+|(?:\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position] ------------------------------------------------ This version keeps your original structure while ensuring that both numbers and operators (with sin, cos, parentheses, etc.) are tokenized correctly.
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | import re class Tokenizer: def __init__(self, input_str): self.tokens = re.findall(r'\d+|(?:\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position] |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | import re class Tokenizer: def __init__(self, input_str): self.tokens = re.findall(r'\d+|(?:\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position] answer = Tokenizer('sin(3+2*4)-cos(15)').tokens expected = ['sin', '(', '3', '+', '2', '*', '4', ')', '-', 'cos', '(', '15', ')'] assert answer == expected, f'Wrong answer; got {answer} instead of {expected}' print('All tests passed') |
All tests passed
Testing if the previous output contains the string All tests passed
: True
Fix this tokenizer keeping it as similar as possible class Tokenizer: def __init__(self, input_str): self.tokens = re.findall(r'\d+|(\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position]
Fix this tokenizer keeping it as similar as possible class Tokenizer: def __init__(self, input_str): self.tokens = re.findall(r'\d+|(\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position]
Below is one acceptable fix. The issue was that the regex used a capturing group for the operators, which causes re.findall to return empty strings for the number tokens. Instead, we can change the capturing group to a non‐capturing group (using (?: … )). This preserves the token order and content: -------------------------------------------------- import re class Tokenizer: def __init__(self, input_str): # Use a non-capturing group for the operators and functions self.tokens = re.findall(r'\d+|(?:\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position] # Example usage: tokenizer = Tokenizer("23+sin(90)") while (token := tokenizer.get_next_token()) is not None: print(token) -------------------------------------------------- This change keeps the tokenizer as similar as possible while fixing the regex behavior.
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | import re class Tokenizer: def __init__(self, input_str): # Use a non-capturing group for the operators and functions self.tokens = re.findall(r'\d+|(?:\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position] |
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 | import re class Tokenizer: def __init__(self, input_str): # Use a non-capturing group for the operators and functions self.tokens = re.findall(r'\d+|(?:\+|\-|\*|/|sin|cos|\(|\))', input_str) self.position = 0 def get_next_token(self): if self.position >= len(self.tokens): return None token = self.tokens[self.position] self.position += 1 return token def peek_next_token(self): if self.position >= len(self.tokens): return None return self.tokens[self.position] answer = Tokenizer('sin(3+2*4)-cos(15)').tokens expected = ['sin', '(', '3', '+', '2', '*', '4', ')', '-', 'cos', '(', '15', ')'] assert answer == expected, f'Wrong answer; got {answer} instead of {expected}' print('All tests passed') |
All tests passed
Testing if the previous output contains the string All tests passed
: True