3 ms·

Should add that C++ has const, making some of this irrelevant. In the C++ case immutability is about making minor changes to a structure more efficient by reusi

Should add that C++ has const, making some of this irrelevant. In the C++ case immutability is about making minor changes to a structure more efficient by reusing the previous version. This is only possible with immutability because you need to be sure that your "base" structure won't change underneath you!

slavik81 7y ago
Can't copy-on-write achieve the same thing? If you keep a reference count, you can know whether it's safe to mutate the underlying data, or whether you need to make a copy first.
- heavenlyblue 7y ago
  Technically copy-on-write is an implementation detail. It may or may not be implemented this way.
  - slavik81 7y ago
    I mean that CoW classes like Qt's QStringList do the same data sharing without being immutable.
    - slavik81 7y ago
      Admittedly, it's pretty easy to accidentally make unnecessary non-const accesses in modern C++. An immutable API would certainly avoid a lot of qAsConst casts.