4 ms·
Both problem could have been solve looooooong ago by introducing a type modifier akin to const that carries if a value is verified (or safe or non-null or other
by pierrebai 6y ago
Both problem could have been solve looooooong ago by introducing a type modifier akin to const that carries if a value is verified (or safe or non-null or other. Pick your synonym).
int * p; // maybe null!
int * verified p; // guaranteed non-null!
A looooong time ago (circa... 1994-1995) I designed a hierarchy of smart pointers and had a variety for non-null so that you could declare a function like:
void foo(non_null_ptr<T>& p);
And know that you don't have to verify for null. All enforced at compile-time. (via the a function on ptr<T> returning a non_null_ptr<T>).
With language support around if() and others, C++ could have mde it even more convenient. Even C could have introduced such a tyupe modifier. Whenever I read about pointers being unsafe and how optionals and maybes are the solution, I roll my eyes, because non-null-ptr do the exact same thing.
The funny thing is C++ has a non-null ptr (with no language support guarantee though): references. Unfortunately, the language made them not resettable, which makes them unusable in many scenario when you'd want them to change value over time, like in most classes members.
- CyberRabbi 6y agoIsn’t “non null optional” the same as just passing the base type?
- pierrebai 6y agoBy reference? Yes. But the idea of a verified type can be extended by using the verified modifier on your own type. For example, you could have a verified matrix type, where the matrix is guaranteed to be valid, non-degenerate. You can apply it to: - matrix - vector - input data of any sort And if teh compiler allowed the programmer to declare their own type modifier, the world is your oyster: you could for example tag that a matrix is a world matrix while another a local matrix and provide a function that converts from one to the other... I wrote a small blog post about the idea: https://www.spiria.com/en/blog/desktop-software/hypothetical-c-extensible-tagging/ https://www.spiria.com/en/blog/desktop-software/hypothetical...
- ubadair 6y agoAre you aware of std::reference_wrapper? https://en.cppreference.com/w/cpp/utility/functional/reference_wrapper https://en.cppreference.com/w/cpp/utility/functional/referen...