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// I want to parameterize a container F as well as the contents A
Mappable<F<A>>

// but type parameters can't have type parameters in Kotlin :-(

// Instead of a type parameter of a type parameter, 
// what if I just use two type parameters?

Mappable<Kind<F,A>>

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fun <T> consumeListOrSequence(mappable: Mappable<T>) {
    mappable.map { it }
}

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fun SingleK.Companion.runtime(ctx: RuntimeContext) = object : Runtime<ForSingleK>(
    SingleK.concurrent(
        object : Dispatchers<ForSingleK> {
            override fun default(): CoroutineContext = Schedulers.computation().asCoroutineContext()

            override fun io(): CoroutineContext = Schedulers.io().asCoroutineContext()
        }
    ), ctx
) {}

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fun IO.Companion.runtime(ctx: RuntimeContext) = object : Runtime<ForIO>(
    IO.concurrent(), ctx
) {}

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fun <F> Runtime<F>.loadNews(): Kind<F, List<NewsItem>>

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@higherkind
sealed class Option<out A> : OptionOf<A> { 
  // snip
}

// the annotation processor will emit the following code for the witness:

// class ForOption private constructor() { companion object }
// typealias OptionOf<A> = arrow.Kind<ForOption, A>

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@extension
interface OptionMappable : Mappable<ForOption> {
  override fun <A, B> OptionOf<A>.map(f: (A) -> B): Option<B> =
    fix().map(f)
}

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interface Mappable<F> {
  fun <A, B> Kind<F, A>.map(f: (A) -> B): Kind<F, B>
}

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class ForOption private constructor() { companion object }
typealias OptionOf<A> = arrow.Kind<ForOption, A>

@Suppress("UNCHECKED_CAST", "NOTHING_TO_INLINE")
inline fun <A> OptionOf<A>.fix(): Option<A> =
  this as Option<A>

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val a: Kind<ForOption, Int> = Option(1)
val fixedA: Option<Int> = a.fix()