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def onTrades[T](trades: List[Trade])(fn: Trade => T) = 
  Future.traverse(trades) {trade =>
    Future { fn(trade) }
  }

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import scalaz._
import Scalaz._

type G[A] = Forall[({type f[B] = ((A, B) => B, B) => B})#f]

val cons: Forall[({type f[A] = (A, Stream[A]) => Stream[A]})#f] =
  new Forall[({type f[A] = (A, Stream[A]) => Stream[A]})#f] {
    def apply[A] = (x, xs) => { println("called cons"); x #:: xs }
  }

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import scalaz._
import Scalaz._

type List[A] = Forall[({type f[B] = ((A, B) => B, B) => B})#f]

val nil: Forall[List] = new Forall[List] {
  def apply[A] = new List[A] {
    def apply[B] = (c, n) => n
  }
}

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http://twitter.com/#!/dgiffone/status/116857796024213504
http://twitter.com/#!/zeit_geist/status/116847468192333825
http://twitter.com/#!/aloyer/status/116858699934470144
http://twitter.com/#!/mich_ham/status/116878614460514305
http://twitter.com/#!/graven/status/116890930707050496

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/**
 * |@| is a helper function that helps you accumulate applicative functors. It gives you an ApplicativeBuilder (it's part of
 * the implementation though) through which you accumulate your applicatives just as you would using the Builder pattern of
 * the GoF in the OO world. Once you have all the applicatives you can pass it a function that will be applied to all the 
 * values that you have accumulated so far. e.g.
 */

scala> (1.some |@| 2.some) apply {_ + _}
res1: Option[Int] = Some(3)

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val m1 = Map(1 -> Map(1 -> "a", 2 -> "b", 3 -> "c"))
val m2 = Map(1 -> Map(2 -> "x"), 2 -> Map(3 -> "d", 5 -> "e"))
tojson(m1) |+| tojson(m2) should equal(tojson(m1 |+| m2))

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trait Cake {
  type Config
  def config: Config
}

trait FooConfig {
  // ...
}

trait FooComponent extends Cake {

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scala> state[Int, Int](10)
res9: scalaz.State[Int,Int] = scalaz.package$State$$anon$1@3bbe242c

scala> res9.run(0)
res10: (Int, Int) = (0,10)

scala> res9 map (_ * 2)
res11: scalaz.StateT[scalaz.Id.Id,Int,Int] = scalaz.StateT$$anon$7@31a9253

scala> res11.run(0)

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Welcome to Scala version 2.10.0-M7 (Java HotSpot(TM) Client VM, Java 1.7.0_01).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import scalaz._
import scalaz._

scala> import Scalaz._
import Scalaz._

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def validAge(age: Int): \/[String, Int] = //..
def validName(name: String): \/[String, String] = //..

(validAge(10).validation.toValidationNEL |@| validName("xxx").validation.toValidationNEL) { (a, n) => //.. }

/**
I am using the above snippet to accumulate errors using scalaz.Either and Validation. Is there any way to do the above without using Validation, just using Either. I don't like the conversion to Validation which I have to do just to lift the errors into a List for accumulation. 
**/