That's a very useful pattern, functional languages often call it the maybe monad. I wish more people used it in other languages. This is my version of it: https://github.com/lorenzhs/algen-framework/blob/master/comm...

That's actually std::optional, minus the nothing/just notation? Indeed more people should use things like this. Reminds me of a similar concept I also have wrappers for: instead of manually having to compare the results of std::find etc against range.end() all over the place, the result is basically in a small container which has both the iterator returned and the end of the range. So I write

    const auto result = alg::find( range, pred );
    if( result )
      doStuff( *result ); //*result is reference to found element

instead of typcial

    const auto end = range.cend();
    const auto result = std::find( range.cbegin(), end, pred );
    if( result != end )
      doStuff( *result );

Not that much of a gain, but once used to it I could never go back. And I realize now this could actually just be rewritten using your maybe class or std::optional.

Yeah it's pretty much std::optional but unfortunately that's in the library fundamentals TS and still in the experimental namespace last I checked. But I have to say that I prefer the name "maybe", it does convey the notion that you have to check whether it's valid much better than "optional" in my opinion.

Yup, this is exactly like Rust's Result<T,E>(with E being std::error_code).