<@U0B8UEMV1> <@U0BRK9HC5> &gt; as for the API, my...

# arrow

[Sherub Thakur]

@pakoito @gildor

as for the API, my suggestion is Either.applicative().map(1.right(), 2.right(), ::plus)

This doesn't work as you need to provide the type info in applicative function
so something like this works

Either.applicative<Either<Int, Int>>().map(Right(1), Right(2)) { (a, b): Tuple2<Int, Int> -> a + b}
But for some reason I can pretty much put any type in there and it works like

Either.applicative<Either<*, *>>().map(Right(1), Right(2)) { (a, b): Tuple2<Int, Int> -> a + b} 
        Either.applicative<Either<String, String>>().map(Right(1), Right(2)) { (a, b): Tuple2<Int, Int> -> a + b}

now but if you do something like this
Either.applicative<Either<Int, Int>>().map(Right(1), Left(2)) { (a, b): Tuple2<Int, Int> -> a + b} // output should be Left(2) as per my understanding of eithers
then it does not work.

What can I read up to understand this behaviour?

I have a situation where I have 2 eithers of types let's say Either<Error, A> and Either<Error, List<B>> and a function with type (A, List<B>) -> C which I want to lift over the 2 eithers so I get Either<Error, C> as output but so far I don't understand what type the applicative function wants.