Interest in contributions for C++23 Monadic functions?

[cmazakas]

https://en.cppreference.com/w/cpp/utility/optional

C++23 added some new monadic functions.

I see these already exist under the names value_or_eval, map and flat_map.

The contribution here would be adding the C++23 compatible member function names and then correspondingly updating the existing tests. Is there any interest in getting something like this included? I'd be volunteering here.

[akrzemi1]

Hi. Thank you for your interest in the library, and for your contribution offer. If I understand correctly, we are talking about adding new names to an already existing functionality, right?

It is worth giving it a thought, however note that Boost.Optional does not aim at 100% compatibility with std::opitonal, for instance:

• it has tag boost::none rather than boost::nullopt,
• it has tag in_place_init rather than in_place (which is reserved in Boost for in-place factories),
• it doesn't have converting constructors between optional<U> and optional<T>, which cause consistency bugs in std::optional

Not to mention that boost::optional offers a bigger interface.
So, the users already have to be aware which optional they are using.

[cmazakas]

If I understand correctly, we are talking about adding new names to an already existing functionality, right?

Yup! This would be so boost::optional is a drop-in replacement and vice versa, acting as a polyfill for eventual C++23 code.

it doesn't have converting constructors between optional and optional, which cause consistency bugs in std::optional

Would you like this as well?

[akrzemi1]

it doesn't have converting constructors between optional and optional, which cause consistency bugs in std::optional

Would you like this as well?

Nope. This converting constructor has a number of gotchas, and is therefore bug prone.

[cmazakas]

Alright, so sounds like a no-go which is cool to me. In the interim, if there's anything you'd like contributions for, just let me know!

I'm going to go ahead and close this issue as it seems resolved to me.

[akrzemi1]

Sure. thanks. For instance, we have this one: #105