Why value changes for bool but not for int using auto

Question

Why value changes for bool but not for int when updated using auto

Please refer code below :

I just took copy of second element from int of vector using auto

As auto does not give direct reference or const without explicitly using it with auto, i expected that change in iVal should not change element value in vector.

This is fine and as per my expectation.

This is not true for bool.... Why am I getting value changed for bool on smililar operation ?
https://code.sololearn.com/cJR4Yk3bm3eZ/?ref=app

Answer 1

The actual answer is that the = operator returns a bool reference, not a bool for vector<bool> ... it is a strange overload, but it is in the vector header.
Reference: https://m.cplusplus.com/reference/vector/vector-bool/reference/
More detailed: https://en.cppreference.com/w/cpp/container/vector/operator%3D

Ignore this below... didn't run the code before answering...
‐--------‐------‐----------------------------------
Hope my code explains it:
https://code.sololearn.com/cpZ1klYcgZ54/?ref=app

TL;DR: you need to think about ehat you actually assign. In C++ almost all types are pure value types. Except for pointers and references, where only a memory location gets assigned to the variable, so you can access the data they point to from multiple locations/variables.

edit: I hope i even got your question right.
i can't see anything unusual about the output. Pordon me if I got the question wrong!

Answer 2

Thanks Erarnitox ... I was confused why bool behaves differently than int

Now got idea about template specialization for bool

Answer 3

Ketan Lalcheta No worries, this is new to me as well, but it seems like vector<bool> is very optimized for space... still that overload does not make too much sense to me, as it is not intuitive, since all other types work differently.
Glad I know about it now myself!

Answer 4

Yeah correct... that much optimization does not make sense at the cost of confusion...