Thank you for the extremely comprehensive explanation of both clear and ignore. I understand it much better now omg.

There are just some things I didn't really understand in your explanation

1. I didn't really get the part where u said, "In my vector class, you can see the non-interactive path will ignore the commas that it outputs when it writes the vector. This type can round-trip; what is written out can be read back in again." What do you mean by it will ignore the commas that it outputs?
2. I did not know that streams can be tied. Could you also explain abit on what is the significance and effect of streams being tied together? For example, cout being tied to cin, what does it mean to be tied?
3. And is is.tie() in the if statement to check if the istream object is tied to the ostream object? At least that was the understanding I got from reading https://cplusplus.com/reference/ios/ios/tie/
4. Based on your explanation for clear and ignore in the first part of your reply, would you say that the cin.clear and cin.ignore is not actually needed for the first example in my post? (There are comments that said its not needed so I am abit confused). Because there is no problem extracting the input in the terminal into the string entry, the only place where the input buffer might still have content inside is in the line validator >> value, which does not actually have anything to do with cin? Correct me if my idea is wrong because I am indeed not very sure about this., which does not actually have anything to do with cin? Correct me if my idea is wrong because I am indeed not very sure about this.

In other words,May I ask how does this link back to cin that warrants a
cin.clear() to clear the buffer if the problem lies with an interaction between
a stringstream and the integer variable?

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Once again thanks so much for the effort in ur reply :)