can I use fx block with `Kind<F, Option<Some...

# arrow

[stojan]

can I use fx block with Kind<F, Option<Something>> where F is MonadError ? (arrow 0.10)?

[stojan]

fx.monad { } did the trick

[Bob Glamm]

fx.monad { } may only enable the Monad combinators; if you were looking to use `catch`/etc. you may need something like fx.monadError (or fx.monadThrow or ...)

[stojan]

got it, thanks

[stojan]

this used to be binding {}

https://github.com/arrow-kt/frdomain.kt/blob/3fce2a090490e9d655358b897e4903cf4331a374/src/main/kotlin/io/arrowkt/tagless/service/interpreter/AccountService.kt#L89

would fx.monad {} be the correct one?

[Bob Glamm]

I would be surprised if the raiseError syntax was enabled in fx.monad {}

[Bob Glamm]

but if it works, it works

[pakoito]

@Bob Glamm the monomorphic versions are enabled, the ones you can import

[raulraja]

Option can only produce a valid monad error instance and that is with Unit

[raulraja]

I’m not even sure we have that in Arrow.

[raulraja]

Essentially None and Unit are isomorphic and Unit can be used to represent the absence over MonadError<F, Unit>

[raulraja]

This instance and if it’s not there it would enable handleErrorWith etc or use Option over where you want to disregard errors in an output.

[raulraja]

The issue is that largely nobody writes polymorphic programs where the E is Unit almost all of our programs are constrained to Throwable and a Explicit hierarchy of E