relax StreamT#trans constraint

scalaz · Aug 2, 2015 · fcc257a · fcc257a
1 parent 4e3ef04
commit fcc257a
Showing 1 changed file with 6 additions and 2 deletions.
diff --git a/core/src/main/scala/scalaz/StreamT.scala b/core/src/main/scala/scalaz/StreamT.scala
@@ -26,8 +26,12 @@ sealed class StreamT[M[_], A](val step: M[StreamT.Step[A, StreamT[M, A]]]) {
 
   def tailM(implicit M: Monad[M]): M[StreamT[M, A]] = M.map(uncons)(_.getOrElse(sys.error("tailM: empty StreamT"))._2)
 
-  def trans[N[_]](t: M ~> N)(implicit M: Monad[M], N: Functor[N]): StreamT[N, A] =
-    StreamTHoist.hoist(t).apply(this)
+  def trans[N[_]](t: M ~> N)(implicit M: Functor[M], N: Functor[N]): StreamT[N, A] =
+    StreamT(t(M.map(this.step)(
+      _( yieldd = (a, as) => Yield(a, as trans t)
+       , skip = as => Skip(as trans t)
+       , done = Done
+       ))))
 
   def filter(p: A => Boolean)(implicit m: Functor[M]): StreamT[M, A] = stepMap {
     _( yieldd = (a, as) => if (p(a)) Yield(a, as filter p) else Skip(as filter p)