MonadError for Either, Option & Try about arrow-core HOT 3 CLOSED

Option's MonadError only works with Unit error types, as we saw early on that it cannot be implemented by a lossy constructors that'd throw that String or any other error type away. It won't pass the MonadError tests.

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Thanks for answering that quick.

When you mean

as we saw early on that it cannot be implemented by a lossy constructors

where that has been describe?

Also I am sorry as new to arrow I am not understanding the

Option's MonadError only works with Unit error types

Could you please provide an example based on the code I put above for being clearer.

Thanks in advance

from arrow-core.

Could you please provide an example based on the code I put above for being clearer.

This is what Option would work with:

private val objectGateway: objectGateway = object : ObjectGateway {

  override fun <F> getObject1(number: String, ME: MonadError<F, Unit>): Kind<F, String> {
    return ME.just("NUMBER")
  }

  override fun <F> getObject2(number: String, anotherNumber: String, ME: MonadError<F, Unit>): Kind<F, Int> {
    return ME.raiseError(Unit)
  }
}

Option has a MonadError<ForOption, Unit>, meaning that you can only build None with Unit. You cannot build None with an associated String or DummyException.

where that has been describe?

In the arrow-contributors channel, early on meaning around 2017 :D

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