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Welcome to twelfth episode of #monadicmonday! Today I want to talk about a Future – a concept of asynchronous lazy task, which is a far better replacement for an eager Promise.
Due to their laziness, futures support cancellation, racing, parallelism and resource safety out of the box. The best library I've seen and used for Futures is fluture-js: github.com/fluture-js/Flu….
Fun fact: in Scala world `Future` is not a monad, but something akin to JS's `Promise` – i.e., eager referentially non-transparent construct. Instead, it's far better to use IO (cats), Task (monix & scalaz) or ZIO (zio) to achieve the described benefits of today's topic.
In `fp-ts` & StaticLand terminology, Future<T> could be described as Task<Either<Error, T>>. But there's much more to it than my simplification implies. So let's dive in!
You have quite a bunch of ways to create a Future. For full list of method go see github.com/fluture-js/Flu…
Please note that due to TS's way of type inference I have to provide type arguments manually:
Please note that due to TS's way of type inference I have to provide type arguments manually:
Why Future is bright and cool? Well, first of all, it is a pure value – i.e., the Future will not be running until you call `fork` or `promise` methods:
Second, Futures support cancellation, making timing out requests a breeze:
Third, Futures are stack-safe:
Fourth, Futures are monads, bifunctors and alternatives, so you can use all the machinery you've used to:
Finally, `fluture` has a nice touch – so kind of imitation for Haskell's `do` notation, available by names `do` and `go`. As a side note, I must admit that attempts to write types for its results are quite cumbersome, but TS can infer them flawlessly:
So as you can see, Futures are a very powerful functional concept, and working with them is really easy thanks to the awesome `fluture-js`! I encourage you to read its documentation and examples, and try it in your projects – it's battle-tested and highly performant.
The documentation for the latest production release is available at github.com/fluture-js/Flu…
This concludes my short introduction to programming with Futures. As usual, all code examples are available at github.com/YBogomolov/mon…
