I disagree with plenty of Andrew's takes as well but I'm with him on private fields. I've never once in 10 years had an issue with a public field that should have been private, however I have had to hack/reimplement entire data structures because some library author thought that no user should touch some private field.
> You cannot reasonably form API contracts (which are the foundation of software modularity) unless you can hide the internal representation. You need to be able to change the internal representation without breaking users.
You never need to hide internal representations to form an "API contract". That doesn't even make sense. If you need to be able to change the internal representation without breaking user code, you're looking for opaque pointers, which have been the solution to this problem since at least C89, I assume earlier.
If you change your data structures or the procedures that operate on them, you're almost certain to break someone's code somewhere, regardless of whether or not you hide the implementation.
> You cannot reasonably form API contracts (which are the foundation of software modularity) unless you can hide the internal representation. You need to be able to change the internal representation without breaking users.
You never need to hide internal representations to form an "API contract". That doesn't even make sense. If you need to be able to change the internal representation without breaking user code, you're looking for opaque pointers, which have been the solution to this problem since at least C89, I assume earlier.
If you change your data structures or the procedures that operate on them, you're almost certain to break someone's code somewhere, regardless of whether or not you hide the implementation.