Hi Brandon, I have been taking a look at your code. I think it is a clever approach. As you have guessed, the implementation of Day is incomplete since there are things that I could not implement for the same reason you state in your gist. The way it works in Kotlin is because they can provide anonymous implementations of interfaces inside methods that capture all type arguments present in the scope; that way, they don't need to carry the extra witness in the type signature as you had to do.
That is the problem we are also having when you try to implement
That is the problem we are also having when you try to implement
Functor for Co. As per its definition, we can only change A to B, but in this case we would also need to transform the existential witness. I am afraid the current encoding we have to simulate HKTs does not allow to do this, or at least I cannot think of a way to do it at the moment.
Hi @truizlop I am going through arrow kit to understand all these functional concepts as I new to Functional world. I am also trying to understand how to write the documentation so as to showcase the advantages of using these construct. This might take some time. In the meantime i have already setup the project and checked on how to write the documentation. If you can provide me some content to refer that might be of help.
Although Twitter seems to be down at the moment
Hi everyone, I've been away from my tests on Bow for some time, but I'm back 🙂 . I would like to play with reader, writer and state monad, but I don't quite understand how to use them 😓. How should I instantiate a Reader Monad with a value that would represent my environment ? and after that, how can I access it ?
ok so
Reader<D, A> is like a plain function (D) -> A
you can usually start with calling the static method
ask to get a Reader<D, D>
and map over the right argument
so, an example using
IO:
protocol Storage {
func save(_ user: User) -> IO<Never, Bool>
}
protocol API {
func fetch(byId: Int) -> IO<Never, User>
}
I can create an structure with the dependencies I am going to need
struct Env {
let database: Storage
let api: API
}
Then, I can write a function with the following signature:
func cacheUser(byId userId: Int) -> ReaderT<IOPartial<Never>, Env, Bool> which means: "Give me a user ID, and I will return a Reader that, when provided an Env will have all it needs to produce IO<Never, Bool>"
Finally, you can run this function by passing an
Env for production, or another one for testing:
let result = try! cacheUser(byId: 1234)
.invoke(Env(database: StorageImpl(),
api: APIImpl()))^
.unsafePerformIO()
I was Thinking of the reader as a Big environment that I had to pass around to my functions
Thank you for your help, I will play with that and see what I can do with it :)
for an example of State, I have a sample in a repo
let me check
from that line on, you can see how I use State to track the inputs and outputs to see the Console has the right interactions
the repo might be outdated though, I'll try to update it when I'm back from vacation
Hello, I was wondering about something, when should someone need to create a new type of monad ? What I want to do is create a data store (kind of like a redux store) where I can act on state if needed to pass it to subcomponent of a swift UI screen.
I was wondering if this was one of the use cases or not.
I was wondering if this was one of the use cases or not.
Monads serve to chain dependent computations and need to obey some rules, so whenever you have that need and can fulfill such rules, you can create a new type with a Monad instance
Hi @truizlop , I was playing around with Bow_Swift and trying to figure out where to use which effect. I have a particular scenario as follows:-
struct User {
let id: String
let name: String
}
protocol Storage {
func get(_ id: String) -> IO<Never, User>
func save(_ user: User) -> IO<Never, Bool>
}
protocol API {
func fetch(byId: Int) -> IO<Never, User>
}
struct UserUsecase {
func getUser(byID id: String) -> What kind of effect can I use here? {
// Get the data from storage
// return the cached data
// fetch the data from API
// save or update the user data from API response
// return back the latest user info
}
}The above function getUserbyID first gets the user data from cache returns that value and in parallel fetched data from API and updates cache and returns back the updates value.
This particular scenario comes a lot in Mobile client application where we cache and update the data from external source.
So What kind of Effect or return type to use here. As any return type can only return once. The only way I can think of is to use Rx Stream. Do we have any other solution or effect to achieve this in a better way?