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

If constness is important to you in this instance I think you probably want to work with immutable types all the way up. Conceptually you'll have a fixed size, const array of const ints. Any time you need to change it (e.g. to add or remove elements, or to sort) you'll need to make a copy of the array with the operation performed and use that instead. While this is very natural in a functional language it doesn't seem quite "right" in C++. getting efficient implementations of sort, for example, could be tricky - but you don't say what you're performance requirements are. Whether you consider this route as being worth it from a performance/ custom code perspective or not I believe it is the correct approach.

After that holding the values by non-const pointer/ smart pointer is probably the best (but has its own overhead, of course).