reason #37 Why macros against Function1->22 would be useful..

ApplicativeMagic.scala

trait ApplicativeMagic[F[_]] {
  def apply[C](f: ApplicativeMagicFunctionHolder[FunctionArg => C]): F[C]
  type FunctionArg
}
class ApplicativeMagicFunctionHolder[F](val f: F)
object ApplicativeMagicFunctionHolder {
  implicit def fix2[A,B,C](f: (A,B) => C): ApplicativeMagicFunctionHolder[Tuple2[A,B] => C] =
    new ApplicativeMagicFunctionHolder({ case (a,b) => f(a,b) })
  implicit def fix3[A,B,C,D](f: (A,B,C) => D): ApplicativeMagicFunctionHolder[Tuple2[Tuple2[A,B],C] => D] = 
    new ApplicativeMagicFunctionHolder({ case ((a,b),c) => f(a,b,c) })
  implicit def fix4[A,B,C,D,E](f: (A,B,C,D) => E): ApplicativeMagicFunctionHolder[Tuple2[Tuple2[Tuple2[A,B],C],D] => E] = 
    new ApplicativeMagicFunctionHolder({ case (((a,b),c),d) => f(a,b,c,d) }) 
  def apply[A,C](f: A => C) = new ApplicativeMagicFunctionHolder(f)
}
object ApplicativeMagic {
  def apply[F[_], A](ma: F[A])(implicit functor: Functor[F]) = new ApplicativeMagic1[F,A](ma)(functor)

}
class ApplicativeMagic1[F[_],A](ma: F[A])(implicit functor: Functor[F]) extends ApplicativeMagic[F] {
  import Implicits._
  type FunctionArg = A
  override def apply[C](f: ApplicativeMagicFunctionHolder[FunctionArg => C]): F[C] = ma map f.f
  def <*>[B](mb: F[B]) = new ApplicativeMagicN[F,B,this.type](mb, this)
}
class ApplicativeMagicN[F[_], B, Magic <: ApplicativeMagic[F]](mn: F[B], prev: Magic)(implicit functor: Functor[F]) extends ApplicativeMagic[F] {
  import Implicits._
  type FunctionArg = (Magic#FunctionArg, B)
  override def apply[C](f: ApplicativeMagicFunctionHolder[FunctionArg => C]): F[C] = {
    val f2: Magic#FunctionArg => B => C = args => b => f.f((args,b))
    mn.fmap(prev[B=>C](ApplicativeMagicFunctionHolder(f2)))
  }
  def <*>[C](mc: F[C]) = new ApplicativeMagicN[F,C,this.type](mc, this)
  
}

usage.repl.scala

scala> ApplicativeMagic(Config("hi")) <*> Config("u") <*> Config("guys") apply (java.sql.DriverManager.getConnection _)
res1: com.github.jsuereth.applicative.config.Config[java.sql.Connection] = com.github.jsuereth.applicative.config.FlatMappedConfig@a0ebdfd

/* Note: Config could also be loaded from file/disk etc.   It's a combined IO/Reader Monad. */