5 files changed, 54 insertions, 15 deletions
diff --git a/src/Text/Hakyll/Context.hs b/src/Text/Hakyll/Context.hs
index d4d3436..11cc123 100644
--- a/src/Text/Hakyll/Context.hs
+++ b/src/Text/Hakyll/Context.hs
@@ -3,6 +3,7 @@ module Text.Hakyll.Context
     ( Context
     , ContextManipulation
     , renderValue
+    , changeValue
     , renderDate
     , changeExtension
     ) where
@@ -23,7 +24,9 @@ type Context = Map String String
 -- | Type for context manipulating functions.
 type ContextManipulation = Context -> Context
 
--- | Do something with a value of a context.
+-- | Do something with a value in a "Context", but keep the old value as well.
+--   This is probably the most common function to construct a
+--   "ContextManipulation".
 renderValue :: String -- ^ Key of which the value should be copied.
             -> String -- ^ Key the value should be copied to.
             -> (String -> String) -- ^ Function to apply on the value.
@@ -32,8 +35,23 @@ renderValue src dst f context = case M.lookup src context of
     Nothing      -> context
     (Just value) -> M.insert dst (f value) context
 
+-- | Change a value in a "Context".
+--
+--   > import Data.Char (toUpper)
+--   > changeValue "title" (map toUpper)
+--
+--   Will put the title in UPPERCASE.
+changeValue :: String -- ^ Key of which the value should be changed.
+            -> (String -> String) -- ^ Function to apply on the value.
+            -> ContextManipulation
+changeValue key = renderValue key key
+
 -- | When the context has a key called @path@ in a @yyyy-mm-dd-title.extension@
 --   format (default for pages), this function can render the date.
+--
+--   > renderDate "date" "%B %e, %Y" "Date unknown"
+--
+--   Will render something like @January 32, 2010@.
 renderDate :: String -- ^ Key in which the rendered date should be placed.
            -> String -- ^ Format to use on the date.
            -> String -- ^ Default value when the date cannot be parsed.
@@ -57,7 +75,8 @@ renderDate key format defaultValue context = M.insert key value context
 --   >                 (createPagePath "test.markdown")
 --
 --   Will render to @test.php@ instead of @test.html@.
-changeExtension :: String -> ContextManipulation
-changeExtension extension = renderValue "url" "url" changeExtension'
+changeExtension :: String -- ^ Extension to change to.
+                   -> ContextManipulation
+changeExtension extension = changeValue "url" changeExtension'
   where
     changeExtension' = flip addExtension extension . dropExtension
diff --git a/src/Text/Hakyll/Page.hs b/src/Text/Hakyll/Page.hs
index 9c319ba..3b76bfd 100644
--- a/src/Text/Hakyll/Page.hs
+++ b/src/Text/Hakyll/Page.hs
@@ -14,7 +14,6 @@ import Data.Maybe (fromMaybe)
 import Control.Monad (liftM)
 import Control.Monad.Reader (liftIO)
 import System.FilePath (takeExtension)
-import System.IO
 
 import Text.Pandoc
 import Data.Binary
diff --git a/src/Text/Hakyll/Render/Internal.hs b/src/Text/Hakyll/Render/Internal.hs
index 27459ad..ecde1d7 100644
--- a/src/Text/Hakyll/Render/Internal.hs
+++ b/src/Text/Hakyll/Render/Internal.hs
@@ -60,7 +60,7 @@ pureRenderWith manipulation template context =
     in body `deepseq` M.insert "body" body context
 
 -- | A pure renderAndConcat function.
-pureRenderAndConcatWith :: ContextManipulation
+pureRenderAndConcatWith :: ContextManipulation -- ^ Manipulation to apply.
                         -> [String] -- ^ Templates to use.
                         -> [Context] -- ^ Different renderables.
                         -> String
diff --git a/src/Text/Hakyll/Tags.hs b/src/Text/Hakyll/Tags.hs
index 4059597..a2031f8 100644
--- a/src/Text/Hakyll/Tags.hs
+++ b/src/Text/Hakyll/Tags.hs
@@ -1,5 +1,19 @@
 -- | Module containing some specialized functions to deal with tags.
 --   This Module follows certain conventions. Stick with them.
+--
+--   More concrete: all functions in this module assume that the tags are
+--   located in the @tags@ field, and separated by commas. An example file
+--   @foo.markdown@ could look like:
+--
+--   > ---
+--   > author: Philip K. Dick
+--   > title: Do androids dream of electric sheep?
+--   > tags: future, science fiction, humanoid
+--   > ---
+--   > The novel is set in a post-apocalyptic near future, where the Earth and
+--   > its populations have been damaged greatly by Nuclear...
+--
+--   All the following functions would work with such a format.
 module Text.Hakyll.Tags
     ( readTagMap
     , renderTagCloud
@@ -12,15 +26,13 @@ import Control.Monad (foldM)
 import Control.Arrow (second)
 
 import Text.Hakyll.Hakyll (Hakyll)
-import Text.Hakyll.Context (ContextManipulation, renderValue)
+import Text.Hakyll.Context (ContextManipulation, changeValue)
 import Text.Hakyll.Render.Internal (finalSubstitute)
 import Text.Hakyll.Regex
 import Text.Hakyll.Util
 import Text.Hakyll.Page
 
--- | Read a tag map. This creates a map from tags to page paths. This function
---   assumes the tags are located in the @tags@ metadata field, separated by
---   commas.
+-- | Read a tag map. This creates a map from tags to page paths.
 readTagMap :: [FilePath] -> Hakyll (M.Map String [FilePath])
 readTagMap paths = foldM addPaths M.empty paths
   where
@@ -59,10 +71,19 @@ renderTagCloud tagMap urlFunction minSize maxSize =
     tagCount :: [(String, Float)]
     tagCount = map (second $ fromIntegral . length) $ M.toList tagMap
 
--- Render all tags to links.
-renderTagLinks :: (String -> String) -- ^ Function that produces an url for a tag.
+-- | Render all tags to links.
+--   
+--   On your side, it is nice if you can display the tags on a page, but
+--   naturally, most people would expect these are clickable.
+--
+--   So, this function takes a function to produce an url for a given tag, and
+--   applies it on all tags.
+--
+--   Note that it is your own responsibility to ensure a page which such an url
+--   exists.
+renderTagLinks :: (String -> String) -- ^ Function to produce an url for a tag.
                -> ContextManipulation
-renderTagLinks urlFunction = renderValue "tags" "tags" renderTagLinks'
+renderTagLinks urlFunction = changeValue "tags" renderTagLinks'
   where
     renderTagLinks' = intercalate ", "
                     . map ((\t -> link t $ urlFunction t) . trim)
diff --git a/src/Text/Hakyll/Util.hs b/src/Text/Hakyll/Util.hs
index 8c33512..5105a31 100644
--- a/src/Text/Hakyll/Util.hs
+++ b/src/Text/Hakyll/Util.hs
@@ -6,20 +6,20 @@ module Text.Hakyll.Util
 
 import Data.Char (isSpace)
 
--- | Trim a string (drop spaces and tabs at both sides).
+-- | Trim a string (drop spaces, tabs and newlines at both sides).
 trim :: String -> String
 trim = reverse . trim' . reverse . trim'
   where
     trim' = dropWhile isSpace
 
--- | Strip html tags.
+-- | Strip html tags from the given string.
 stripHTML :: String -> String
 stripHTML []  = []
 stripHTML str = let (beforeTag, rest) = break (== '<') str
                     (_, afterTag)     = break (== '>') rest
                 in beforeTag ++ stripHTML (tail' afterTag)
-    -- We need a failsafe tail function.
   where
+    -- We need a failsafe tail function.
     tail' [] = []
     tail' xs = tail xs