3 files changed, 32 insertions, 18 deletions
diff --git a/src/Hakyll/Core/Compiler.hs b/src/Hakyll/Core/Compiler.hs
index e1eab79..840f3bd 100644
--- a/src/Hakyll/Core/Compiler.hs
+++ b/src/Hakyll/Core/Compiler.hs
@@ -108,7 +108,6 @@ module Hakyll.Core.Compiler
     , cached
     , unsafeCompiler
     , traceShowCompiler
-    , mapCompiler
     , timedCompiler
     , byPattern
     , byExtension
@@ -328,12 +327,6 @@ traceShowCompiler = fromJob $ \x -> CompilerM $ do
     report logger $ show x
     return x
 
--- | Map over a compiler
---
-mapCompiler :: Compiler a b
-            -> Compiler [a] [b]
-mapCompiler (Compiler d j) = Compiler d $ mapM j
-
 -- | Log and time a compiler
 --
 timedCompiler :: String        -- ^ Message
diff --git a/src/Hakyll/Core/Compiler/Internal.hs b/src/Hakyll/Core/Compiler/Internal.hs
index acdfe80..2a3342f 100644
--- a/src/Hakyll/Core/Compiler/Internal.hs
+++ b/src/Hakyll/Core/Compiler/Internal.hs
@@ -38,6 +38,7 @@ import           Hakyll.Core.Logger
 import           Hakyll.Core.ResourceProvider
 import           Hakyll.Core.Routes
 import           Hakyll.Core.Store
+import           Hakyll.Core.Util.Arrow
 
 
 --------------------------------------------------------------------------------
@@ -139,6 +140,11 @@ instance ArrowChoice Compiler where
 
 
 --------------------------------------------------------------------------------
+instance ArrowMap Compiler where
+    mapA (Compiler d j) = Compiler d $ mapM j
+
+
+--------------------------------------------------------------------------------
 -- | Run a compiler, yielding the resulting target
 runCompilerJob :: Compiler () a     -- ^ Compiler to run
                -> Identifier ()     -- ^ Target identifier
diff --git a/src/Hakyll/Core/Util/Arrow.hs b/src/Hakyll/Core/Util/Arrow.hs
index f46d083..96a5e09 100644
--- a/src/Hakyll/Core/Util/Arrow.hs
+++ b/src/Hakyll/Core/Util/Arrow.hs
@@ -1,25 +1,40 @@
+--------------------------------------------------------------------------------
 -- | Various arrow utility functions
---
 module Hakyll.Core.Util.Arrow
-    ( constA
+    ( ArrowMap (..)
+    , constA
     , sequenceA
     , unitA
     ) where
 
-import Control.Arrow (Arrow, (&&&), arr, (>>^))
 
-constA :: Arrow a
-       => c
-       -> a b c
+--------------------------------------------------------------------------------
+import           Control.Arrow (Arrow, ArrowChoice, arr, (&&&), (>>^))
+
+
+--------------------------------------------------------------------------------
+-- | Additional arrow typeclass for performance reasons.
+class ArrowChoice a => ArrowMap a where
+    mapA :: a b c -> a [b] [c]
+
+
+--------------------------------------------------------------------------------
+instance ArrowMap (->) where
+    mapA = map
+
+
+--------------------------------------------------------------------------------
+constA :: Arrow a => c -> a b c
 constA = arr . const
 
-sequenceA :: Arrow a
-          => [a b c]
-          -> a b [c]
+
+--------------------------------------------------------------------------------
+sequenceA :: Arrow a => [a b c] -> a b [c]
 sequenceA = foldr reduce $ constA []
   where
     reduce xa la = xa &&& la >>^ arr (uncurry (:))
 
-unitA :: Arrow a
-      => a b ()
+
+--------------------------------------------------------------------------------
+unitA :: Arrow a => a b ()
 unitA = constA ()