Hello everyone, after implementing `scala.Functio...

# kotlin-spark

[zeugederunity]

Hello everyone,

after implementing scala.Function1 i recognized that Kotlin has problems with overriding traits.

If you use it as functional interface, you get a Kotlin: Interface Function1 does not have constructors error:

ScalaFunction1<Any, String> {
    ('A'.toInt()+(it as Int)).toChar().toString()
}

If you implement it as anonymous object you get the error Kotlin: Object is not abstract and does not implement abstract member public abstract fun <A : Any!> compose(p0: Function1<A!, Any!>!): Function1<A!, String!>! defined in scala.Function1 :

private fun tabulateIntToStringFunc() = object : ScalaFunction1<Any, String> {
    override fun apply(v1: Any?): String {
        return ('A'.toInt()+(v1 as Int)).toChar().toString()
    }
}

If you implement andThen and compose you get the error `Kotlin: Object is not abstract and does not implement abstract member public abstract fun `apply$mcZD$sp`(p0: Double): Boolean defined in scala.Function1` :

private fun tabulateIntToStringFunc() = object : ScalaFunction1<Any, String> {
    override fun apply(v1: Any?): String {
        return ('A'.toInt()+(v1 as Int)).toChar().toString()
    }

    override fun <A : Any?> andThen(g: scala.Function1<String, A>?): scala.Function1<Any, A> {
        throw NotImplementedError()
    }

    override fun <A : Any?> compose(g: scala.Function1<A, Any>?): scala.Function1<A, String> {
        throw NotImplementedError()
    }
}

But it is not possible to override this abstract function.
Can someone explain to me what is happening there? I'm new to this Scala-Kotlin business, i think this lack of knowledge is my core-problem here. Furthermore i don't know the inner working mechanisms of Scala and its java-interop, which adds even more challenges for me. ^^'

[zeugederunity]

Found the class scala.runtime.AbstractFunctionN , allowing to use FunctionN . But i don't get, why there are these "ghost functions" when implementing a trait.

[asm0dey]

Oh I'm so sorry I've missed this thread!

Coud you please provide me with info on why do you need this?