Can I use const in vectors to allow adding elements, but not modifications to the already added?

Question

My comments on this answer got me thinking about the issues of constness and sorting. I played around a bit and reduced my issues to the fact that this code:

Answer 1

I've been thinking a bit on this issue and it seems that you requirement is off.

You don't want to add immutable values to your vector:

std::vector vec = /**/;
std::vector::const_iterator first = vec.begin();

std::sort(vec.begin(), vec.end());

assert(*vec.begin() == *first); // false, even though `const int`

What you really want is your vector to hold a constant collection of values, in a modifiable order, which cannot be expressed by the std::vector syntax even if it worked.

I am afraid that it's an extremely specified task that would require a dedicated class.