Add recover and recoverWith

[Thomvis]

Would you be open to adding recover and recoverWith to Result. They're similar to map and flatMap except that they are given closures that run when the Result failed and then provide an opportunity to make it succeed. The implementation of recover would actually be identical to the ?? operation.

If you are favorable of this change, I'd like to make a PR.

For more context, see Thomvis/BrightFutures#49, where we're discussing to replace a custom Result implementation with this library and identify the functions discussed here as the biggest missing piece.

The naming comes from Scala (http://www.scala-lang.org/api/2.10.1/index.html#scala.concurrent.Future), at least that's where I got it from.

[robrix]

Thanks for filing this!

I’m of two minds. Against:

• I really like reinforcing use of the extant ?? operator—overloading is very much in Swift’s idiom, and the analogy between Result’s ?? and Optional’s is clear, and supportive of general use of the language. Adding recover/recoverWith dilutes that somewhat, and so I’m a bit reluctant.

For:

• ?? doesn’t cover recoverWith, and an ?? overload taking a function on the right hand side feels like it’s too distinct in usage from the extant overloads to be reasonably named ??, and I don’t much want to define new custom operators.
• recover and recoverWith are pretty decent names with some precedent, and names are searchable where operators are not; for which reason (in part) we have flatMap as well as >>-.

On the balance, I think it’d make a fine addition. My only request is that the documentation for recover mention the equivalence with ??.

Thank you kindly!

[robrix]

Fixed by #42. I’ll tag in a moment.

[Thomvis]

@robrix Thanks for the fast response & thanks @nvh for the PR 🌟

[nvh]

🎉 ❤️

[robrix]

You’re very welcome 😄