and so until you complete your N steps

and then

@dh44t uploaded a file: Untitled

but the crucial point is

you need to design very well your type

S

of

State<S, A>

cause that type most be able to carry all the data needed from one step to the next one

ok that makes sense, and the docs do a good job of showing how to chain together those steps ill have give it some more thought and try and understand both

State

and

StateT

usage more i havent had that aha moment (yet!), but i like to think im getting closer - thanks @dh44t

👋

@yousuf.haque not that I'm aware of.

Hi! 👋 I would like to keep in a data type either an integer id to a resource, or a string value. as I imagine, using

Either

for this would be a heresy, since the Left value wouldn’t be used for errors in my case. Is there any other data type in arrow that represents an “exclusive-or” relationship, but that better fits my use case? Thanks!

It's perfectly OK to use Either for that

I'd model the most frequent used value or happy path in the Right and the other on the Left

What does the String value represent if it was an actual type?

it’s just a label for an Android text view

I’m pretty new to functional programming, so I hope I am doing this right 😁

I think we all wonder that about ourselves but you are most welcome here!

Is the label used to print something about an error or exceptional case?

kind of, yes, it’s to display the state, like empty or error message

and I would like to be able to use resource IDs for generic messages. it’s better for i18n on Android to do it that way

So, you are using the string value only if you don't have a resource ID? Like a missing localization key fallback?

that, or showing an error message from the server, for instance

I see, I'd model it without either then as a simple ADT:

sealed class DisplayStrategy
data class DefaultLabel(value: String): DisplayStrategy()
data class LocalizedLabel(int: ResourceId): DisplayStrategy()

fun bizLogic(): DisplayStrategy

A sealed hierarchy is also a disjoint union and you can give it whatever semantics and as many cases as you want

makes sense 🙂

ADTs are a type and all it's possible states

perfect for recursion, build optimizations and add combinators like

fold

,

map

etc... on top of them

which will lead you into type classes and other areas of FP that solve other problems

yes, I would have to implement those myself, which I was trying to avoid by using something premade similar to

Either

, haha

in many cases you can auto derive them with Arrow

@simon.vergauwen wrote for example

@autofold