Merge pull request scalaz#203 into scalaz-seven

.gitignore

@@ -9,3 +9,4 @@ tags
 *~
 *#
 z_local.sbt
+.DS_Store

concurrent/src/main/scala/scalaz/concurrent/BooleanLatch.scala

@@ -32,4 +32,4 @@ object BooleanLatch {
     override def release() = sync release 0
     override def await() = sync acquireInterruptibly 0
   }
-}
+}

core/src/main/scala/scalaz/Bitraverse.scala

@@ -68,7 +68,7 @@ trait Bitraverse[F[_, _]] extends Bifunctor[F] with Bifoldable[F] { self =>
   def traverseSTrampoline[S, G[_] : Applicative, A, B, C, D](fa: F[A, B])(f: A => State[S, G[C]])(g: B => State[S, G[D]]): State[S, G[F[C, D]]] = {
     import Free._
     implicit val A = StateT.stateTMonadState[S, Trampoline].compose(Applicative[G])
-    bitraverse[({type λ[α]=StateT[Trampoline, S, G[α]]})#λ, A, B, C, D](fa)(f(_: A).lift[Trampoline])(g(_: B).lift[Trampoline]).unliftId[Trampoline, G[F[C, D]]]
+    bitraverse[({type λ[α]=StateT[Trampoline, S, G[α]]})#λ, A, B, C, D](fa)(f(_: A).lift[Trampoline])(g(_: B).lift[Trampoline]).unliftId[Trampoline, G[F[C, D]], S, S]
   }
 
   /** Bitraverse `fa` with a `Kleisli[G, S, C]` and `Kleisli[G, S, D]`, internally using a `Trampoline` to avoid stack overflow. */

core/src/main/scala/scalaz/Cojoin.scala

@@ -28,6 +28,8 @@ object Cojoin {
     self: Cobind[F] =>
 
     def cojoin[A](fa: F[A]): F[F[A]] = cobind(fa)(fa => fa)
+
+    override def extend[A, B](a: F[A])(f: F[A] => B): F[B] = cobind(a)(f)
   }
 
   ////

core/src/main/scala/scalaz/ComonadCoState.scala

@@ -3,11 +3,20 @@ package scalaz
 trait ComonadStore[F[_, _], S] extends Comonad[({type f[x]=F[S,x]})#f] {
   def pos[A](w: F[S, A]): S
   def peek[A](s: S, w: F[S, A]): A
-  def peeks[A](s: S => S, w: F[S, A]): A
-  def seek[A](s: S, w: F[S, A]): F[S, A]
-  def seeks[A](s: S => S, w: F[S, A]): F[S, A]
+
+  def peeks[A](s: S => S, w: F[S, A]): A =
+    peek(s(pos(w)), w)
+
+  def seek[A](s: S, w: F[S, A]): F[S, A] =
+    peek(s, cojoin(w))
+
+  def seeks[A](s: S => S, w: F[S, A]): F[S, A] =
+    peeks(s, cojoin(w))
+
+  def experiment[G[_], A](s: S => G[S], w: F[S, A])(implicit FG: Functor[G]): G[A] =
+    FG.map(s(pos(w)))(peek(_, w))
 }
 
 object ComonadStore {
-  def apply[F[_,_],S](implicit F: ComonadStore[F, S]) = F
+  def apply[F[_, _],S](implicit F: ComonadStore[F, S]): ComonadStore[F, S] = F
 }

core/src/main/scala/scalaz/ComonadTrans.scala

@@ -11,3 +11,7 @@ object ComonadTrans {
 trait Cohoist[F[_[_], _]] extends ComonadTrans[F] {
   def cohoist[M[_], N[_]: Comonad](f: M ~> N): ({type f[x] = F[M, x]})#f ~> ({type f[x] = F[N, x]})#f
 }
+
+object Cohoist {
+  def apply[F[_[_], _]](implicit F: Cohoist[F]): Cohoist[F] = F
+}