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Full implementation of ScalacApplicativeBuilder
package io.scalac
import shapeless._
import shapeless.ops.function.FnToProduct
import shapeless.ops.hlist.Tupler
import scala.languageFeature.implicitConversions
import scalaz.Monad
import scalaz.syntax.ToMonadOps
package object shapelessmonad {
trait IsHListOfM[M[_], In <: HList, Out <: HList] extends ToMonadOps{
def hsequence(l: In): M[Out]
}
object IsHListOfM {
def apply[M[_], In <: HList, Out <: HList](implicit isHM: IsHListOfM[M, In, Out], m: Monad[M]): IsHListOfM[M, In, Out] = isHM
implicit def IsHNilHListOfM[M[_]](implicit m: Monad[M]) = new IsHListOfM[M, HNil, HNil] {
override def hsequence(l: HNil): M[HNil] = m.pure(HNil)
}
implicit def hconsIsHListOfM[M[_], H, In <: HList, Out <: HList](implicit ev: IsHListOfM[M, In, Out], m: Monad[M]): IsHListOfM[M, M[H] :: In, H :: Out] = new IsHListOfM[M, M[H] :: In, H :: Out] {
override def hsequence(l: M[H] :: In): M[H :: Out] =
l.head.flatMap(h => ev.hsequence(l.tail).map(h :: _))
}
}
def hsequence[M[_], In <: HList, Out <: HList](l: In)(implicit ev: IsHListOfM[M, In, Out], m: Monad[M]) = ev.hsequence(l)
case class ScalacApplicativeBuilder[M[_], In <: HList, Out <: HList](values: In)(implicit m: Monad[M]) {
def asTuple[T](implicit ev: IsHListOfM[M, In, Out], m: Monad[M], tupler: Tupler.Aux[Out, T]): M[T] = m.map(hsequence(values))(_.tupled)
def apply[F, FOut](f: F)(implicit fnEv: FnToProduct.Aux[F, Out => FOut], ev: IsHListOfM[M, In, Out]): M[FOut] =
m.map(hsequence(values))(fnEv(f))
def :@:[X, T1](newOne: M[X]) = ScalacApplicativeBuilder[M, M[X] :: In, X :: Out](newOne :: values)
}
implicit def ToScalacApplicativeBuilder[M[_], V](value: M[V])(implicit ev: IsHListOfM[M, M[V] :: HNil, V :: HNil], m: Monad[M]): ScalacApplicativeBuilder[M, M[V] :: HNil, V::HNil] =
new ScalacApplicativeBuilder[M, M[V] :: HNil, V :: HNil](value :: HNil)
}
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