diff --git a/quiver.cabal b/quiver.cabal
--- a/quiver.cabal
+++ b/quiver.cabal
@@ -1,5 +1,5 @@
 name:           quiver
-version:        0.0.0.2
+version:        0.0.0.3
 synopsis:       Quiver finite stream processing library
 homepage:       https://github.com/zadarnowski/quiver
 category:       Control
@@ -35,7 +35,7 @@
 source-repository this
   type:         git
   location:     https://github.com/zadarnowski/quiver.git
-  tag:          0.0.0.2
+  tag:          0.0.0.3
 
 library
   hs-source-dirs:   src
diff --git a/src/Control/Quiver.lhs b/src/Control/Quiver.lhs
--- a/src/Control/Quiver.lhs
+++ b/src/Control/Quiver.lhs
@@ -20,6 +20,7 @@
 >   fetch, fetch',
 >   emit, emit', emit_,
 >   liftP,
+>   runEffect,
 >   (>>->), (>->>),
 > ) where
 
@@ -71,6 +72,18 @@
 
 > liftP :: Functor f => f r -> P a' a b' b f r
 > liftP = enclose . fmap deliver
+
+> -- | Evaluates an /effect/, i.e., a processor that is both detached
+> --   and depleted and hence neither consumes nor produces any input,
+> --   returning its delivered value. The base functor must be a monad.
+
+> runEffect :: Monad f => Effect f r -> f r
+> runEffect p = loop p
+>  where
+>   loop (Consume _ _ q) = loop q
+>   loop (Produce _ _ q) = loop q
+>   loop (Enclose f)     = f >>= loop
+>   loop (Deliver r)     = return r
 
 > -- | The @>>->@ represents a push-based composition of stream processor.
 > --   @p1 >>-> p2@ represents a stream processor that forwards the output