[jonhohle]

IMHO the mapping issue comes from functions not being first class, so all types require Functor-like interfaces which are needlessly verbose. Splitting these is not semantically different than a function that returns a value vs a function that returns a Result.

I have little love for Java, but explicitly typed checked exceptions are something I miss frequently in other languages.

[dwohnitmok]

No I think it's a deeper issue than that. In particular because exceptions aren't a return value, you can't make a function generic over both values and exceptions at the same time. This would persist even with first class functions.

If you want to be generic over exceptions, you have to throw an exception. It would be nice to have e.g. a single `map` method that appropriately throws an exception when the function that is called throws a function and one that doesn't throw an exception when the function that is called throws a function. But as it stands, if you want to be able to throw a checked exception at all, you have to mark that your higher order function throws checked exceptions, even if you would prefer to be more generic so that e.g. you only throw a checked exception if your function that is called throws a checked exception.

[jonhohle]

Thr only reason this works in other languages is because they’ve made the choice to return objects that represent success+value or error and then added explicit syntax to support those types. That means function signatures put the error in the return type instead of a separate exception channel, but that’s really only a syntactic difference. It’s otherwise isomorphic.