4 ms·

Here's a much simpler example of something impossible in C++ and trivial in Rust: how about a non-nullable unique_ptr? The constructor should just be able to ch

Here's a much simpler example of something impossible in C++ and trivial in Rust: how about a non-nullable unique_ptr? The constructor should just be able to check for null and then no code need ever check for null again, right? Sorry, you need an invalid state to represent a moved-from instance, so this is impossible. Are you telling me that having to accommodate invalid states that are semantically both unnecessary and undesirable is not a serious limitation of C++ move semantics?

fluoridation 3y ago
Following the previous example, you wrap std::unique_ptr in another class that has no move constructor and forwards constructor parameters to std::make_unique(), and can also be constructed from an std::unique_ptr. Now you have a heap-allocated smart pointer class that can't possibly be null. Alternatively, you make it movable, and if someone tries to call operator*(), operator->(), or get() on the null value, you throw an exception. Not as clean, but, hey, it's safe.