From 99200aef5d99a9ffe1c9c98fc9d31db4a78d2e26 Mon Sep 17 00:00:00 2001
From: Jasper Van der Jeugt <m@jaspervdj.be>
Date: Wed, 26 Dec 2012 15:00:45 +0100
Subject: Foldable/Traversable instance for Item

---
 src/Hakyll/Core/Item.hs               | 30 ++++++++++++++++++++++++------
 src/Hakyll/Core/UnixFilter.hs         |  6 +++---
 tests/Hakyll/Core/UnixFilter/Tests.hs |  2 +-
 3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/src/Hakyll/Core/Item.hs b/src/Hakyll/Core/Item.hs
index ccf9e9a..8933d5b 100644
--- a/src/Hakyll/Core/Item.hs
+++ b/src/Hakyll/Core/Item.hs
@@ -5,17 +5,21 @@
 module Hakyll.Core.Item
     ( Item (..)
     , itemSetBody
-    , itemM
+    , withItemBody
     ) where
 
 
 --------------------------------------------------------------------------------
-import           Control.Applicative    ((<$>), (<*>))
-import           Data.Binary            (Binary (..))
-import           Data.Typeable          (Typeable)
+import           Control.Applicative           (Applicative, (<$>), (<*>))
+import           Data.Binary                   (Binary (..))
+import           Data.Foldable                 (Foldable (..))
+import           Data.Traversable              (Traversable (..))
+import           Data.Typeable                 (Typeable)
+import           Prelude                       hiding (foldr)
 
 
 --------------------------------------------------------------------------------
+import           Hakyll.Core.Compiler.Internal
 import           Hakyll.Core.Identifier
 
 
@@ -31,6 +35,16 @@ instance Functor Item where
     fmap f (Item i x) = Item i (f x)
 
 
+--------------------------------------------------------------------------------
+instance Foldable Item where
+    foldr f z (Item _ x) = f x z
+
+
+--------------------------------------------------------------------------------
+instance Traversable Item where
+    traverse f (Item i x) = Item i <$> f x
+
+
 --------------------------------------------------------------------------------
 instance Binary a => Binary (Item a) where
     put (Item i x) = put i >> put x
@@ -43,5 +57,9 @@ itemSetBody x (Item i _) = Item i x
 
 
 --------------------------------------------------------------------------------
-itemM :: Monad m => (a -> m b) -> Item a -> m (Item b)
-itemM f (Item i b) = f b >>= \b' -> return (Item i b')
+-- | Perform a compiler action on the item body. This is the same as 'traverse',
+-- but looks less intimidating.
+--
+-- > withItemBody = traverse
+withItemBody :: (a -> Compiler b) -> Item a -> Compiler (Item b)
+withItemBody = traverse
diff --git a/src/Hakyll/Core/UnixFilter.hs b/src/Hakyll/Core/UnixFilter.hs
index dc82366..e493aee 100644
--- a/src/Hakyll/Core/UnixFilter.hs
+++ b/src/Hakyll/Core/UnixFilter.hs
@@ -26,7 +26,7 @@ import           Hakyll.Core.Compiler
 -- as a compiler.
 --
 -- > rev :: Compiler String
--- > rev = getResourceString >>= itemM (unixFilter "rev" [])
+-- > rev = getResourceString >>= withItemBody (unixFilter "rev" [])
 --
 -- A more realistic example: one can use this to call, for example, the sass
 -- compiler on CSS files. More information about sass can be found here:
@@ -38,7 +38,7 @@ import           Hakyll.Core.Compiler
 -- > match "style.scss" $ do
 -- >     route   $ setExtension "css"
 -- >     compile $ getResourceString >>=
--- >         itemM (unixFilter "sass" ["-s", "--scss"]) >>=
+-- >         withItemBody (unixFilter "sass" ["-s", "--scss"]) >>=
 -- >         compressCssCompiler
 unixFilter :: String           -- ^ Program name
            -> [String]         -- ^ Program args
@@ -59,7 +59,7 @@ unixFilter = unixFilterWith writer reader
 --
 -- > match "music.wav" $ do
 -- >     route   $ setExtension "ogg"
--- >     compile $ getResourceLBS >>= unixFilter "oggenc" ["-"]
+-- >     compile $ getResourceLBS >>= withItemBody (unixFilter "oggenc" ["-"])
 unixFilterLBS :: String               -- ^ Program name
               -> [String]             -- ^ Program args
               -> ByteString           -- ^ Program input
diff --git a/tests/Hakyll/Core/UnixFilter/Tests.hs b/tests/Hakyll/Core/UnixFilter/Tests.hs
index f5cbf9d..c3e1c99 100644
--- a/tests/Hakyll/Core/UnixFilter/Tests.hs
+++ b/tests/Hakyll/Core/UnixFilter/Tests.hs
@@ -33,5 +33,5 @@ unixFilterRev = withTestStore $ \store -> do
     expected <- testCompilerDone store provider "russian.md" getResourceString
     H.assert $ rev (itemBody expected) == lines (itemBody output)
   where
-    compiler = getResourceString >>= itemM (unixFilter "rev" [])
+    compiler = getResourceString >>= withItemBody (unixFilter "rev" [])
     rev      = map reverse . lines
-- 
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