20 files changed, 115 insertions, 126 deletions
diff --git a/src/Text/Pandoc/Writers/CommonMark.hs b/src/Text/Pandoc/Writers/CommonMark.hs
index e991cd384..66ded218f 100644
--- a/src/Text/Pandoc/Writers/CommonMark.hs
+++ b/src/Text/Pandoc/Writers/CommonMark.hs
@@ -1,5 +1,3 @@
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE ViewPatterns      #-}
 {- |
    Module      : Text.Pandoc.Writers.CommonMark
    Copyright   : Copyright (C) 2015-2020 John MacFarlane
diff --git a/src/Text/Pandoc/Writers/ConTeXt.hs b/src/Text/Pandoc/Writers/ConTeXt.hs
index 7bae37a79..0a6313513 100644
--- a/src/Text/Pandoc/Writers/ConTeXt.hs
+++ b/src/Text/Pandoc/Writers/ConTeXt.hs
@@ -209,7 +209,7 @@ blockToConTeXt (Div (ident,_,kvs) bs) = do
                                      <> literal lng <> "]" $$ txt $$ "\\stop"
                        Nothing  -> txt
       wrapBlank txt = blankline <> txt <> blankline
-  (wrapBlank . wrapLang . wrapDir . wrapRef) <$> blockListToConTeXt bs
+  wrapBlank . wrapLang . wrapDir . wrapRef <$> blockListToConTeXt bs
 blockToConTeXt (BulletList lst) = do
   contents <- mapM listItemToConTeXt lst
   return $ ("\\startitemize" <> if isTightList lst
@@ -332,7 +332,7 @@ alignToConTeXt align = case align of
                          AlignDefault -> empty
 
 listItemToConTeXt :: PandocMonad m => [Block] -> WM m (Doc Text)
-listItemToConTeXt list = (("\\item" $$) . nest 2) <$> blockListToConTeXt list
+listItemToConTeXt list = ("\\item" $$) . nest 2 <$> blockListToConTeXt list
 
 defListItemToConTeXt :: PandocMonad m => ([Inline], [[Block]]) -> WM m (Doc Text)
 defListItemToConTeXt (term, defs) = do
@@ -487,7 +487,7 @@ inlineToConTeXt (Span (_,_,kvs) ils) = do
                        Just lng -> braces ("\\language" <>
                                            brackets (literal lng) <> txt)
                        Nothing -> txt
-  (wrapLang . wrapDir) <$> inlineListToConTeXt ils
+  wrapLang . wrapDir <$> inlineListToConTeXt ils
 
 -- | Craft the section header, inserting the section reference, if supplied.
 sectionHeader :: PandocMonad m
diff --git a/src/Text/Pandoc/Writers/Docbook.hs b/src/Text/Pandoc/Writers/Docbook.hs
index d3517159f..408d8cc0c 100644
--- a/src/Text/Pandoc/Writers/Docbook.hs
+++ b/src/Text/Pandoc/Writers/Docbook.hs
@@ -179,7 +179,7 @@ blockToDocbook opts (Div (id',"section":_,_) (Header lvl _ ils : xs)) = do
 blockToDocbook opts (Div (ident,_,_) [Para lst]) =
   let attribs = [("id", ident) | not (T.null ident)] in
   if hasLineBreaks lst
-     then (flush . nowrap . inTags False "literallayout" attribs)
+     then flush . nowrap . inTags False "literallayout" attribs
                          <$> inlinesToDocbook opts lst
      else inTags True "para" attribs <$> inlinesToDocbook opts lst
 blockToDocbook opts (Div (ident,_,_) bs) = do
@@ -206,7 +206,7 @@ blockToDocbook opts (Para [Image attr txt (src,T.stripPrefix "fig:" -> Just _)])
              (imageToDocbook opts attr src) $$
            inTagsSimple "textobject" (inTagsSimple "phrase" alt))
 blockToDocbook opts (Para lst)
-  | hasLineBreaks lst = (flush . nowrap . inTagsSimple "literallayout")
+  | hasLineBreaks lst = flush . nowrap . inTagsSimple "literallayout"
                         <$> inlinesToDocbook opts lst
   | otherwise         = inTagsIndented "para" <$> inlinesToDocbook opts lst
 blockToDocbook opts (LineBlock lns) =
@@ -277,7 +277,7 @@ blockToDocbook opts (Table _ blkCapt specs thead tbody tfoot) = do
   head' <- if all null headers
               then return empty
               else inTagsIndented "thead" <$> tableRowToDocbook opts headers
-  body' <- (inTagsIndented "tbody" . vcat) <$>
+  body' <- inTagsIndented "tbody" . vcat <$>
               mapM (tableRowToDocbook opts) rows
   return $ inTagsIndented tableType $ captionDoc $$
         inTags True "tgroup" [("cols", tshow (length aligns))] (
@@ -305,14 +305,14 @@ tableRowToDocbook :: PandocMonad m
                   -> [[Block]]
                   -> DB m (Doc Text)
 tableRowToDocbook opts cols =
-  (inTagsIndented "row" . vcat) <$> mapM (tableItemToDocbook opts) cols
+  inTagsIndented "row" . vcat <$> mapM (tableItemToDocbook opts) cols
 
 tableItemToDocbook :: PandocMonad m
                    => WriterOptions
                    -> [Block]
                    -> DB m (Doc Text)
 tableItemToDocbook opts item =
-  (inTags True "entry" [] . vcat) <$> mapM (blockToDocbook opts) item
+  inTags True "entry" [] . vcat <$> mapM (blockToDocbook opts) item
 
 -- | Convert a list of inline elements to Docbook.
 inlinesToDocbook :: PandocMonad m => WriterOptions -> [Inline] -> DB m (Doc Text)
diff --git a/src/Text/Pandoc/Writers/Docx.hs b/src/Text/Pandoc/Writers/Docx.hs
index 81dbb6ce0..fa7e2ceea 100644
--- a/src/Text/Pandoc/Writers/Docx.hs
+++ b/src/Text/Pandoc/Writers/Docx.hs
@@ -1030,7 +1030,7 @@ blockToOpenXML' opts (Table _ blkCapt specs thead tbody tfoot) = do
   let rowwidth = fullrow * sum widths
   let mkgridcol w = mknode "w:gridCol"
                        [("w:w", show (floor (textwidth * w) :: Integer))] ()
-  let hasHeader = any (not . null) headers
+  let hasHeader = not $ all null headers
   modify $ \s -> s { stInTable = False }
   return $
     caption' ++
diff --git a/src/Text/Pandoc/Writers/EPUB.hs b/src/Text/Pandoc/Writers/EPUB.hs
index 63034a577..12004889f 100644
--- a/src/Text/Pandoc/Writers/EPUB.hs
+++ b/src/Text/Pandoc/Writers/EPUB.hs
@@ -62,7 +62,7 @@ import Text.DocTemplates (FromContext(lookupContext), Context(..),
                           ToContext(toVal), Val(..))
 
 -- A Chapter includes a list of blocks.
-data Chapter = Chapter [Block]
+newtype Chapter = Chapter [Block]
   deriving (Show)
 
 data EPUBState = EPUBState {
@@ -711,10 +711,10 @@ pandocToEPUB version opts doc = do
                          | writerTableOfContents opts ] ++
                   map chapterRefNode chapterEntries)
           , unode "guide" $
-             [ unode "reference" !
-                   [("type","toc"),("title", tocTitle),
-                    ("href","nav.xhtml")] $ ()
-             ] ++
+             (unode "reference" !
+                 [("type","toc"),("title", tocTitle),
+                  ("href","nav.xhtml")] $ ()
+             ) :
              [ unode "reference" !
                    [("type","cover")
                    ,("title","Cover")
@@ -838,14 +838,12 @@ pandocToEPUB version opts doc = do
                                 ] | writerTableOfContents opts
                               ]
                          else []
-  let landmarks = if null landmarkItems
-                     then []
-                     else [RawBlock (Format "html") $ TS.pack $ ppElement $
-                            unode "nav" ! [("epub:type","landmarks")
-                                          ,("id","landmarks")
-                                          ,("hidden","hidden")] $
-                            [ unode "ol" landmarkItems ]
-                          ]
+  let landmarks = [RawBlock (Format "html") $ TS.pack $ ppElement $
+                    unode "nav" ! [("epub:type","landmarks")
+                                  ,("id","landmarks")
+                                  ,("hidden","hidden")] $
+                    [ unode "ol" landmarkItems ]
+                  | not (null landmarkItems)]
   navData <- lift $ writeHtml opts'{ writerVariables =
                      Context (M.fromList [("navpage", toVal' "true")])
                      <> cssvars False <> vars }
@@ -940,7 +938,7 @@ metadataElement version md currentTime =
           | version == EPUB2 = [dcNode "identifier" !
               (("id",id') : maybe [] (\x -> [("opf:scheme", x)]) scheme) $
               txt]
-          | otherwise = [dcNode "identifier" ! [("id",id')] $ txt] ++
+          | otherwise = (dcNode "identifier" ! [("id",id')] $ txt) :
               maybe [] ((\x -> [unode "meta" !
                                 [ ("refines",'#':id')
                                 , ("property","identifier-type")
diff --git a/src/Text/Pandoc/Writers/HTML.hs b/src/Text/Pandoc/Writers/HTML.hs
index 6bb708c37..decc487c1 100644
--- a/src/Text/Pandoc/Writers/HTML.hs
+++ b/src/Text/Pandoc/Writers/HTML.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE LambdaCase          #-}
 {-# LANGUAGE MultiWayIf          #-}
 {-# LANGUAGE OverloadedStrings   #-}
@@ -1025,7 +1024,7 @@ rowListToHtml :: PandocMonad m
               -> [TableRow]
               -> StateT WriterState m Html
 rowListToHtml opts rows =
-  (\x -> (nl opts *> mconcat x)) <$>
+  (\x -> nl opts *> mconcat x) <$>
      mapM (tableRowToHtml opts) rows
 
 colSpecListToHtml :: PandocMonad m
diff --git a/src/Text/Pandoc/Writers/Haddock.hs b/src/Text/Pandoc/Writers/Haddock.hs
index 9d8c5ec41..aaa19ed07 100644
--- a/src/Text/Pandoc/Writers/Haddock.hs
+++ b/src/Text/Pandoc/Writers/Haddock.hs
@@ -28,7 +28,7 @@ import Text.Pandoc.Templates (renderTemplate)
 import Text.Pandoc.Writers.Shared
 
 type Notes = [[Block]]
-data WriterState = WriterState { stNotes :: Notes }
+newtype WriterState = WriterState { stNotes :: Notes }
 instance Default WriterState
   where def = WriterState{ stNotes = [] }
 
diff --git a/src/Text/Pandoc/Writers/JATS.hs b/src/Text/Pandoc/Writers/JATS.hs
index 50ce04e03..4dc02d686 100644
--- a/src/Text/Pandoc/Writers/JATS.hs
+++ b/src/Text/Pandoc/Writers/JATS.hs
@@ -216,7 +216,7 @@ imageMimeType src kvs =
                   (T.takeWhile (/='/') <$> mbMT)
       subtype = fromMaybe "" $
                   lookup "mime-subtype" kvs `mplus`
-                  ((T.drop 1 . T.dropWhile (/='/')) <$> mbMT)
+                  (T.drop 1 . T.dropWhile (/='/') <$> mbMT)
   in (maintype, subtype)
 
 languageFor :: [Text] -> Text
@@ -372,7 +372,7 @@ blockToJATS opts (Table _ blkCapt specs th tb tf) =
       thead <- if all null headers
                   then return empty
                   else inTagsIndented "thead" <$> tableRowToJATS opts True headers
-      tbody <- (inTagsIndented "tbody" . vcat) <$>
+      tbody <- inTagsIndented "tbody" . vcat <$>
                     mapM (tableRowToJATS opts False) rows
       return $ inTags True "table" [] $ coltags $$ thead $$ tbody
 
@@ -389,7 +389,7 @@ tableRowToJATS :: PandocMonad m
                   -> [[Block]]
                   -> JATS m (Doc Text)
 tableRowToJATS opts isHeader cols =
-  (inTagsIndented "tr" . vcat) <$> mapM (tableItemToJATS opts isHeader) cols
+  inTagsIndented "tr" . vcat <$> mapM (tableItemToJATS opts isHeader) cols
 
 tableItemToJATS :: PandocMonad m
                    => WriterOptions
@@ -400,7 +400,7 @@ tableItemToJATS opts isHeader [Plain item] =
   inTags False (if isHeader then "th" else "td") [] <$>
     inlinesToJATS opts item
 tableItemToJATS opts isHeader item =
-  (inTags False (if isHeader then "th" else "td") [] . vcat) <$>
+  inTags False (if isHeader then "th" else "td") [] . vcat <$>
     mapM (blockToJATS opts) item
 
 -- | Convert a list of inline elements to JATS.
@@ -547,7 +547,7 @@ inlineToJATS _ (Image (ident,_,kvs) _ (src, tit)) = do
                   (T.takeWhile (/='/') <$> mbMT)
   let subtype = fromMaybe "" $
                   lookup "mime-subtype" kvs `mplus`
-                  ((T.drop 1 . T.dropWhile (/='/')) <$> mbMT)
+                  (T.drop 1 . T.dropWhile (/='/') <$> mbMT)
   let attr = [("id", ident) | not (T.null ident)] ++
              [("mimetype", maintype),
               ("mime-subtype", subtype),
diff --git a/src/Text/Pandoc/Writers/LaTeX.hs b/src/Text/Pandoc/Writers/LaTeX.hs
index 3753604db..071a288e1 100644
--- a/src/Text/Pandoc/Writers/LaTeX.hs
+++ b/src/Text/Pandoc/Writers/LaTeX.hs
@@ -1049,7 +1049,7 @@ wrapDiv (_,classes,kvs) t = do
                            let valign = maybe "T" mapAlignment (lookup "align" kvs)
                                totalwidth = maybe [] (\x -> ["totalwidth=" <> x])
                                  (lookup "totalwidth" kvs)
-                               onlytextwidth = filter ((==) "onlytextwidth") classes
+                               onlytextwidth = filter ("onlytextwidth" ==) classes
                                options = text $ T.unpack $ T.intercalate "," $
                                  valign : totalwidth ++ onlytextwidth 
                            in inCmd "begin" "columns" <> brackets options
@@ -1458,8 +1458,8 @@ citeArgumentsList (CiteGroup _ _ []) = return empty
 citeArgumentsList (CiteGroup pfxs sfxs ids) = do
       pdoc <- inlineListToLaTeX pfxs
       sdoc <- inlineListToLaTeX sfxs'
-      return $ (optargs pdoc sdoc) <>
-              (braces (literal (T.intercalate "," (reverse ids))))
+      return $ optargs pdoc sdoc <>
+              braces (literal (T.intercalate "," (reverse ids)))
       where sfxs' = stripLocatorBraces $ case sfxs of
                 (Str t : r) -> case T.uncons t of
                   Just (x, xs)
@@ -1516,12 +1516,12 @@ citationsToBiblatex (c:cs)
 
       groups <- mapM citeArgumentsList (reverse (foldl' grouper [] (c:cs)))
 
-      return $ text cmd <> (mconcat groups)
+      return $ text cmd <> mconcat groups
 
   where grouper prev cit = case prev of
          ((CiteGroup oPfx oSfx ids):rest)
-             | null oSfx && null pfx -> (CiteGroup oPfx sfx (cid:ids)):rest
-         _ -> (CiteGroup pfx sfx [cid]):prev
+             | null oSfx && null pfx -> CiteGroup oPfx sfx (cid:ids) : rest
+         _ -> CiteGroup pfx sfx [cid] : prev
          where pfx = citationPrefix cit
                sfx = citationSuffix cit
                cid = citationId cit
diff --git a/src/Text/Pandoc/Writers/Man.hs b/src/Text/Pandoc/Writers/Man.hs
index 62449431c..4eb0db042 100644
--- a/src/Text/Pandoc/Writers/Man.hs
+++ b/src/Text/Pandoc/Writers/Man.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE LambdaCase        #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE ViewPatterns      #-}
 {- |
@@ -232,8 +233,7 @@ definitionListItemToMan opts (label, defs) = do
   labelText <- inlineListToMan opts $ makeCodeBold label
   contents <- if null defs
                  then return empty
-                 else liftM vcat $ forM defs $ \blocks ->
-                        case blocks of
+                 else liftM vcat $ forM defs $ \case
                           (x:xs) -> do
                             first' <- blockToMan opts $
                                       case x of
diff --git a/src/Text/Pandoc/Writers/Markdown.hs b/src/Text/Pandoc/Writers/Markdown.hs
index 3e50704ca..323d159b0 100644
--- a/src/Text/Pandoc/Writers/Markdown.hs
+++ b/src/Text/Pandoc/Writers/Markdown.hs
@@ -24,10 +24,9 @@ import Control.Monad.Reader
 import Control.Monad.State.Strict
 import Data.Char (isAlphaNum)
 import Data.Default
-import Data.List (find, intersperse, sortBy, transpose)
+import Data.List (find, intersperse, sortOn, transpose)
 import qualified Data.Map as M
 import Data.Maybe (fromMaybe, mapMaybe)
-import Data.Ord (comparing)
 import qualified Data.Set as Set
 import Data.Text (Text)
 import qualified Data.Text as T
@@ -127,7 +126,7 @@ pandocTitleBlock tit auths dat =
 
 mmdTitleBlock :: Context Text -> Doc Text
 mmdTitleBlock (Context hashmap) =
-  vcat $ map go $ sortBy (comparing fst) $ M.toList hashmap
+  vcat $ map go $ sortOn fst $ M.toList hashmap
   where go (k,v) =
           case (text (T.unpack k), v) of
                (k', ListVal xs)
@@ -148,15 +147,15 @@ mmdTitleBlock (Context hashmap) =
 plainTitleBlock :: Doc Text -> [Doc Text] -> Doc Text -> Doc Text
 plainTitleBlock tit auths dat =
   tit <> cr <>
-  (hcat (intersperse (text "; ") auths)) <> cr <>
+  hcat (intersperse (text "; ") auths) <> cr <>
   dat <> cr
 
 yamlMetadataBlock :: Context Text -> Doc Text
-yamlMetadataBlock v = "---" $$ (contextToYaml v) $$ "---"
+yamlMetadataBlock v = "---" $$ contextToYaml v $$ "---"
 
 contextToYaml :: Context Text -> Doc Text
 contextToYaml (Context o) =
-  vcat $ map keyvalToYaml $ sortBy (comparing fst) $ M.toList o
+  vcat $ map keyvalToYaml $ sortOn fst $ M.toList o
  where
   keyvalToYaml (k,v) =
           case (text (T.unpack k), v) of
@@ -250,7 +249,7 @@ pandocToMarkdown opts (Pandoc meta blocks) = do
 
 -- | Return markdown representation of reference key table.
 refsToMarkdown :: PandocMonad m => WriterOptions -> Refs -> MD m (Doc Text)
-refsToMarkdown opts refs = mapM (keyToMarkdown opts) refs >>= return . vcat
+refsToMarkdown opts refs = vcat <$> mapM (keyToMarkdown opts) refs
 
 -- | Return markdown representation of a reference key.
 keyToMarkdown :: PandocMonad m
@@ -446,7 +445,7 @@ blockToMarkdown' opts (Plain inlines) = do
            then inlines
            else case inlines of
                   (Str t:ys)
-                    | (null ys || startsWithSpace ys)
+                    | null ys || startsWithSpace ys
                     , beginsWithOrderedListMarker t
                     -> RawInline (Format "markdown") (escapeMarker t):ys
                   (Str t:_)
@@ -462,7 +461,7 @@ blockToMarkdown' opts (Para [Image attr alt (src,tgt@(T.stripPrefix "fig:" -> Ju
   | isEnabled Ext_raw_html opts &&
     not (isEnabled Ext_link_attributes opts) &&
     attr /= nullAttr = -- use raw HTML
-    ((<> blankline) . literal . T.strip) <$>
+    (<> blankline) . literal . T.strip <$>
       writeHtml5String opts{ writerTemplate = Nothing }
         (Pandoc nullMeta [Para [Image attr alt (src,tgt)]])
   | otherwise = blockToMarkdown opts (Para [Image attr alt (src,tit)])
@@ -472,7 +471,7 @@ blockToMarkdown' opts (LineBlock lns) =
   if isEnabled Ext_line_blocks opts
   then do
     mdLines <- mapM (inlineListToMarkdown opts) lns
-    return $ (vcat $ map (hang 2 (literal "| ")) mdLines) <> blankline
+    return $ vcat (map (hang 2 (literal "| ")) mdLines) <> blankline
   else blockToMarkdown opts $ linesToPara lns
 blockToMarkdown' opts b@(RawBlock f str) = do
   variant <- asks envVariant
@@ -582,28 +581,28 @@ blockToMarkdown' opts (CodeBlock attribs str) = do
          attrs  = if isEnabled Ext_fenced_code_attributes opts
                      then nowrap $ " " <> attrsToMarkdown attribs
                      else case attribs of
-                                (_,(cls:_),_) -> " " <> literal cls
+                                (_,cls:_,_) -> " " <> literal cls
                                 _             -> empty
 blockToMarkdown' opts (BlockQuote blocks) = do
   variant <- asks envVariant
   -- if we're writing literate haskell, put a space before the bird tracks
   -- so they won't be interpreted as lhs...
-  let leader = if isEnabled Ext_literate_haskell opts
-                  then " > "
-                  else if variant == PlainText then "  " else "> "
+  let leader
+        | isEnabled Ext_literate_haskell opts = " > "
+        | variant == PlainText = "  "
+        | otherwise            = "> "
   contents <- blockListToMarkdown opts blocks
-  return $ (prefixed leader contents) <> blankline
+  return $ prefixed leader contents <> blankline
 blockToMarkdown' opts t@(Table _ blkCapt specs thead tbody tfoot) = do
   let (caption, aligns, widths, headers, rows) = toLegacyTable blkCapt specs thead tbody tfoot
   let numcols = maximum (length aligns : length widths :
                            map length (headers:rows))
   caption' <- inlineListToMarkdown opts caption
-  let caption'' = if null caption
-                     then blankline
-                     else
-                       if isEnabled Ext_table_captions opts
-                          then blankline $$ (": " <> caption') $$ blankline
-                          else blankline $$ caption' $$ blankline
+  let caption''
+        | null caption = blankline
+        | isEnabled Ext_table_captions opts
+        = blankline $$ (": " <> caption') $$ blankline
+        | otherwise = blankline $$ caption' $$ blankline
   let hasSimpleCells = onlySimpleTableCells $ headers : rows
   let isSimple = hasSimpleCells && all (==0) widths
   let isPlainBlock (Plain _) = True
@@ -652,7 +651,7 @@ blockToMarkdown' opts t@(Table _ blkCapt specs thead tbody tfoot) = do
                 (id,) <$> pipeTable (all null headers) aligns' rawHeaders rawRows
             | isEnabled Ext_raw_html opts -> fmap (id,) $
                    literal <$>
-                   (writeHtml5String opts{ writerTemplate = Nothing } $ Pandoc nullMeta [t])
+                   writeHtml5String opts{ writerTemplate = Nothing } (Pandoc nullMeta [t])
             | otherwise -> return (id, literal "[TABLE]")
   return $ nst (tbl $$ caption'') $$ blankline
 blockToMarkdown' opts (BulletList items) = do
@@ -680,7 +679,7 @@ inList p = local (\env -> env {envInList = True}) p
 addMarkdownAttribute :: Text -> Text
 addMarkdownAttribute s =
   case span isTagText $ reverse $ parseTags s of
-       (xs,(TagOpen t attrs:rest)) ->
+       (xs, TagOpen t attrs:rest) ->
             renderTags' $ reverse rest ++ (TagOpen t attrs' : reverse xs)
               where attrs' = ("markdown","1"):[(x,y) | (x,y) <- attrs,
                                  x /= "markdown"]
@@ -745,17 +744,16 @@ pandocTable opts multiline headless aligns widths rawHeaders rawRows = do
         | isSimple  = map numChars columns
         | otherwise = zipWith relWidth widths columns
   let makeRow = hcat . intersperse (lblock 1 (literal " ")) .
-                   (zipWith3 alignHeader aligns widthsInChars)
+                   zipWith3 alignHeader aligns widthsInChars
   let rows' = map makeRow rawRows
   let head' = makeRow rawHeaders
   let underline = mconcat $ intersperse (literal " ") $
                   map (\width -> literal (T.replicate width "-")) widthsInChars
-  let border = if multiline
-                  then literal (T.replicate (sum widthsInChars +
-                          length widthsInChars - 1) "-")
-                  else if headless
-                          then underline
-                          else empty
+  let border
+        | multiline = literal (T.replicate (sum widthsInChars +
+                        length widthsInChars - 1) "-")
+        | headless  = underline
+        | otherwise = empty
   let head'' = if headless
                   then empty
                   else border <> cr <> head'
@@ -890,18 +888,17 @@ blockListToMarkdown opts blocks = do
       isListBlock (OrderedList _ _)  = True
       isListBlock (DefinitionList _) = True
       isListBlock _                  = False
-      commentSep  = if variant == PlainText
-                       then Null
-                       else if isEnabled Ext_raw_html opts
-                            then RawBlock "html" "<!-- -->\n"
-                            else RawBlock "markdown" "&nbsp;\n"
-  mapM (blockToMarkdown opts) (fixBlocks blocks) >>= return . mconcat
+      commentSep
+        | variant == PlainText        = Null
+        | isEnabled Ext_raw_html opts = RawBlock "html" "<!-- -->\n"
+        | otherwise                   = RawBlock "markdown" "&nbsp;\n"
+  mconcat <$> mapM (blockToMarkdown opts) (fixBlocks blocks)
 
 getKey :: Doc Text -> Key
 getKey = toKey . render Nothing
 
 findUsableIndex :: [Text] -> Int -> Int
-findUsableIndex lbls i = if (tshow i) `elem` lbls
+findUsableIndex lbls i = if tshow i `elem` lbls
                          then findUsableIndex lbls (i + 1)
                          else i
 
@@ -973,19 +970,19 @@ inlineListToMarkdown opts lst = do
   go (if inlist then avoidBadWrapsInList lst else lst)
   where go [] = return empty
         go (i:is) = case i of
-            (Link _ _ _) -> case is of
+            Link {} -> case is of
                 -- If a link is followed by another link, or '[', '(' or ':'
                 -- then we don't shortcut
-                (Link _ _ _):_                                  -> unshortcutable
-                Space:(Link _ _ _):_                            -> unshortcutable
+                Link {}:_                                       -> unshortcutable
+                Space:Link {}:_                                 -> unshortcutable
                 Space:(Str(thead -> Just '[')):_                -> unshortcutable
                 Space:(RawInline _ (thead -> Just '[')):_       -> unshortcutable
                 Space:(Cite _ _):_                              -> unshortcutable
-                SoftBreak:(Link _ _ _):_                        -> unshortcutable
+                SoftBreak:Link {}:_                             -> unshortcutable
                 SoftBreak:(Str(thead -> Just '[')):_            -> unshortcutable
                 SoftBreak:(RawInline _ (thead -> Just '[')):_   -> unshortcutable
                 SoftBreak:(Cite _ _):_                          -> unshortcutable
-                LineBreak:(Link _ _ _):_                        -> unshortcutable
+                LineBreak:Link {}:_                             -> unshortcutable
                 LineBreak:(Str(thead -> Just '[')):_            -> unshortcutable
                 LineBreak:(RawInline _ (thead -> Just '[')):_   -> unshortcutable
                 LineBreak:(Cite _ _):_                          -> unshortcutable
@@ -1016,16 +1013,16 @@ avoidBadWrapsInList :: [Inline] -> [Inline]
 avoidBadWrapsInList [] = []
 avoidBadWrapsInList (s:Str (T.uncons -> Just ('>',cs)):xs) | isSp s =
   Str (" >" <> cs) : avoidBadWrapsInList xs
-avoidBadWrapsInList (s:Str (T.uncons -> Just (c, cs)):[])
-  | T.null cs && isSp s && c `elem` ['-','*','+'] = Str (T.pack [' ', c]) : []
+avoidBadWrapsInList [s, Str (T.uncons -> Just (c, cs))]
+  | T.null cs && isSp s && c `elem` ['-','*','+'] = [Str $ T.pack [' ', c]]
 avoidBadWrapsInList (s:Str (T.uncons -> Just (c, cs)):Space:xs)
   | T.null cs && isSp s && c `elem` ['-','*','+'] =
     Str (T.pack [' ', c]) : Space : avoidBadWrapsInList xs
 avoidBadWrapsInList (s:Str cs:Space:xs)
   | isSp s && isOrderedListMarker cs =
     Str (" " <> cs) : Space : avoidBadWrapsInList xs
-avoidBadWrapsInList (s:Str cs:[])
-  | isSp s && isOrderedListMarker cs = Str (" " <> cs) : []
+avoidBadWrapsInList [s, Str cs]
+  | isSp s && isOrderedListMarker cs = [Str $ " " <> cs]
 avoidBadWrapsInList (x:xs) = x : avoidBadWrapsInList xs
 
 isOrderedListMarker :: Text -> Bool
@@ -1105,7 +1102,7 @@ inlineToMarkdown opts (Strikeout lst) = do
                        else contents
 inlineToMarkdown _ (Superscript []) = return empty
 inlineToMarkdown opts (Superscript lst) =
-  local (\env -> env {envEscapeSpaces = (envVariant env == Markdown)}) $ do
+  local (\env -> env {envEscapeSpaces = envVariant env == Markdown}) $ do
     contents <- inlineListToMarkdown opts lst
     if isEnabled Ext_superscript opts
        then return $ "^" <> contents <> "^"
@@ -1123,7 +1120,7 @@ inlineToMarkdown opts (Superscript lst) =
                            Nothing -> literal $ "^(" <> rendered <> ")"
 inlineToMarkdown _ (Subscript []) = return empty
 inlineToMarkdown opts (Subscript lst) =
-  local (\env -> env {envEscapeSpaces = (envVariant env == Markdown)}) $ do
+  local (\env -> env {envEscapeSpaces = envVariant env == Markdown}) $ do
     contents <- inlineListToMarkdown opts lst
     if isEnabled Ext_subscript opts
        then return $ "~" <> contents <> "~"
@@ -1167,7 +1164,7 @@ inlineToMarkdown opts (Code attr str) = do
                      then 0
                      else maximum $ map T.length tickGroups
   let marker     = T.replicate (longest + 1) "`"
-  let spacer     = if (longest == 0) then "" else " "
+  let spacer     = if longest == 0 then "" else " "
   let attrs      = if isEnabled Ext_inline_code_attributes opts && attr /= nullAttr
                       then attrsToMarkdown attr
                       else empty
@@ -1296,7 +1293,7 @@ inlineToMarkdown opts lnk@(Link attr txt (src, tit))
   | isEnabled Ext_raw_html opts &&
     not (isEnabled Ext_link_attributes opts) &&
     attr /= nullAttr = -- use raw HTML
-    (literal . T.strip) <$>
+    literal . T.strip <$>
       writeHtml5String opts{ writerTemplate = Nothing } (Pandoc nullMeta [Plain [lnk]])
   | otherwise = do
   variant <- asks envVariant
@@ -1337,7 +1334,7 @@ inlineToMarkdown opts img@(Image attr alternate (source, tit))
   | isEnabled Ext_raw_html opts &&
     not (isEnabled Ext_link_attributes opts) &&
     attr /= nullAttr = -- use raw HTML
-    (literal . T.strip) <$>
+    literal . T.strip <$>
       writeHtml5String opts{ writerTemplate = Nothing } (Pandoc nullMeta [Plain [img]])
   | otherwise = do
   variant <- asks envVariant
@@ -1352,7 +1349,7 @@ inlineToMarkdown opts img@(Image attr alternate (source, tit))
 inlineToMarkdown opts (Note contents) = do
   modify (\st -> st{ stNotes = contents : stNotes st })
   st <- get
-  let ref = literal $ writerIdentifierPrefix opts <> tshow (stNoteNum st + (length $ stNotes st) - 1)
+  let ref = literal $ writerIdentifierPrefix opts <> tshow (stNoteNum st + length (stNotes st) - 1)
   if isEnabled Ext_footnotes opts
      then return $ "[^" <> ref <> "]"
      else return $ "[" <> ref <> "]"
diff --git a/src/Text/Pandoc/Writers/Ms.hs b/src/Text/Pandoc/Writers/Ms.hs
index 561053c88..f3aadde59 100644
--- a/src/Text/Pandoc/Writers/Ms.hs
+++ b/src/Text/Pandoc/Writers/Ms.hs
@@ -67,9 +67,7 @@ pandocToMs opts (Pandoc meta blocks) = do
   let authorsMeta = map (escapeStr opts . stringify) $ docAuthors meta
   hasHighlighting <- gets stHighlighting
   let highlightingMacros = if hasHighlighting
-                              then case writerHighlightStyle opts of
-                                        Nothing  -> mempty
-                                        Just sty -> styleToMs sty
+                              then maybe mempty styleToMs $ writerHighlightStyle opts
                               else mempty
 
   let context = defField "body" main
@@ -523,7 +521,7 @@ msFormatter opts _fmtopts =
  where
   fmtLine = mconcat . map fmtToken
   fmtToken (toktype, tok) =
-    "\\*[" <> (tshow toktype) <> " \"" <> (escapeStr opts tok) <> "\"]"
+    "\\*[" <> tshow toktype <> " \"" <> escapeStr opts tok <> "\"]"
 
 highlightCode :: PandocMonad m => WriterOptions -> Attr -> Text -> MS m (Doc Text)
 highlightCode opts attr str =
diff --git a/src/Text/Pandoc/Writers/ODT.hs b/src/Text/Pandoc/Writers/ODT.hs
index 36fa7a4c1..e41fb7176 100644
--- a/src/Text/Pandoc/Writers/ODT.hs
+++ b/src/Text/Pandoc/Writers/ODT.hs
@@ -71,7 +71,7 @@ pandocToODT opts doc@(Pandoc meta _) = do
   refArchive <-
        case writerReferenceDoc opts of
              Just f -> liftM toArchive $ lift $ P.readFileLazy f
-             Nothing -> lift $ (toArchive . B.fromStrict) <$>
+             Nothing -> lift $ toArchive . B.fromStrict <$>
                                 P.readDataFile "reference.odt"
   -- handle formulas and pictures
   -- picEntriesRef <- P.newIORef ([] :: [Entry])
diff --git a/src/Text/Pandoc/Writers/OPML.hs b/src/Text/Pandoc/Writers/OPML.hs
index 3edf2daa3..810a94775 100644
--- a/src/Text/Pandoc/Writers/OPML.hs
+++ b/src/Text/Pandoc/Writers/OPML.hs
@@ -40,7 +40,7 @@ writeOPML opts (Pandoc meta blocks) = do
                 writeMarkdown def (Pandoc nullMeta [Plain ils]))
               meta'
   let blocks' = makeSections False (Just 1) blocks
-  main <- (render colwidth . vcat) <$>
+  main <- render colwidth . vcat <$>
              mapM (blockToOPML opts) blocks'
   let context = defField "body" main metadata
   return $
diff --git a/src/Text/Pandoc/Writers/OpenDocument.hs b/src/Text/Pandoc/Writers/OpenDocument.hs
index c6b66382b..bd20d2db6 100644
--- a/src/Text/Pandoc/Writers/OpenDocument.hs
+++ b/src/Text/Pandoc/Writers/OpenDocument.hs
@@ -387,7 +387,7 @@ blockToOpenDocument o bs
                            r <- vcat  <$> mapM (deflistItemToOpenDocument o) b
                            setInDefinitionList False
                            return r
-      preformatted  s = (flush . vcat) <$> mapM (inPreformattedTags . escapeStringForXML) (T.lines s)
+      preformatted  s = flush . vcat <$> mapM (inPreformattedTags . escapeStringForXML) (T.lines s)
       mkBlockQuote  b = do increaseIndent
                            i <- paraStyle
                                  [("style:parent-style-name","Quotations")]
diff --git a/src/Text/Pandoc/Writers/Powerpoint/Output.hs b/src/Text/Pandoc/Writers/Powerpoint/Output.hs
index 656ef6056..603a84acc 100644
--- a/src/Text/Pandoc/Writers/Powerpoint/Output.hs
+++ b/src/Text/Pandoc/Writers/Powerpoint/Output.hs
@@ -303,11 +303,11 @@ makeSpeakerNotesMap (Presentation _ slides) =
 
 presentationToArchive :: PandocMonad m => WriterOptions -> Presentation -> m Archive
 presentationToArchive opts pres = do
-  distArchive <- (toArchive . BL.fromStrict) <$>
+  distArchive <- toArchive . BL.fromStrict <$>
                       P.readDefaultDataFile "reference.pptx"
   refArchive <- case writerReferenceDoc opts of
                      Just f  -> toArchive <$> P.readFileLazy f
-                     Nothing -> (toArchive . BL.fromStrict) <$>
+                     Nothing -> toArchive . BL.fromStrict <$>
                         P.readDataFile "reference.pptx"
 
   utctime <- P.getCurrentTime
@@ -351,10 +351,10 @@ curSlideHasSpeakerNotes =
 getLayout :: PandocMonad m => Layout -> P m Element
 getLayout layout = do
   let layoutpath = case layout of
-        (MetadataSlide{}) -> "ppt/slideLayouts/slideLayout1.xml"
-        (TitleSlide _)          -> "ppt/slideLayouts/slideLayout3.xml"
-        (ContentSlide _ _)      -> "ppt/slideLayouts/slideLayout2.xml"
-        (TwoColumnSlide{})    -> "ppt/slideLayouts/slideLayout4.xml"
+        MetadataSlide{}  -> "ppt/slideLayouts/slideLayout1.xml"
+        TitleSlide{}     -> "ppt/slideLayouts/slideLayout3.xml"
+        ContentSlide{}   -> "ppt/slideLayouts/slideLayout2.xml"
+        TwoColumnSlide{} -> "ppt/slideLayouts/slideLayout4.xml"
   refArchive <- asks envRefArchive
   distArchive <- asks envDistArchive
   parseXml refArchive distArchive layoutpath
@@ -547,7 +547,7 @@ registerMedia fp caption = do
 
 makeMediaEntry :: PandocMonad m => MediaInfo -> P m Entry
 makeMediaEntry mInfo = do
-  epochtime <- (floor . utcTimeToPOSIXSeconds) <$> asks envUTCTime
+  epochtime <- floor . utcTimeToPOSIXSeconds <$> asks envUTCTime
   (imgBytes, _) <- P.fetchItem (T.pack $ mInfoFilePath mInfo)
   let ext = fromMaybe "" (mInfoExt mInfo)
   let fp = "ppt/media/image" <>
@@ -1473,7 +1473,7 @@ presentationToRelsEntry pres = do
 
 elemToEntry :: PandocMonad m => FilePath -> Element -> P m Entry
 elemToEntry fp element = do
-  epochtime <- (floor . utcTimeToPOSIXSeconds) <$> asks envUTCTime
+  epochtime <- floor . utcTimeToPOSIXSeconds <$> asks envUTCTime
   return $ toEntry fp epochtime $ renderXml element
 
 slideToEntry :: PandocMonad m => Slide -> P m Entry
@@ -1500,8 +1500,7 @@ slideToSpeakerNotesEntry slide = do
 
 slideToSpeakerNotesRelElement :: PandocMonad m => Slide -> P m (Maybe Element)
 slideToSpeakerNotesRelElement (Slide _ _ (SpeakerNotes [])) = return Nothing
-slideToSpeakerNotesRelElement slide@(
-  Slide{}) = do
+slideToSpeakerNotesRelElement slide@Slide{} = do
   idNum <- slideNum slide
   return $ Just $
     mknode "Relationships"
@@ -1585,10 +1584,10 @@ slideToSlideRelElement :: PandocMonad m => Slide -> P m Element
 slideToSlideRelElement slide = do
   idNum <- slideNum slide
   let target =  case slide of
-        (Slide _ (MetadataSlide{}) _) -> "../slideLayouts/slideLayout1.xml"
-        (Slide _ (TitleSlide _) _)          -> "../slideLayouts/slideLayout3.xml"
-        (Slide _ (ContentSlide _ _) _)      -> "../slideLayouts/slideLayout2.xml"
-        (Slide _ (TwoColumnSlide{}) _)  -> "../slideLayouts/slideLayout4.xml"
+        (Slide _ MetadataSlide{} _)  -> "../slideLayouts/slideLayout1.xml"
+        (Slide _ TitleSlide{} _)     -> "../slideLayouts/slideLayout3.xml"
+        (Slide _ ContentSlide{} _)   -> "../slideLayouts/slideLayout2.xml"
+        (Slide _ TwoColumnSlide{} _) -> "../slideLayouts/slideLayout4.xml"
 
   speakerNotesRels <- maybeToList <$> speakerNotesSlideRelElement slide
 
@@ -1819,7 +1818,7 @@ getSpeakerNotesFilePaths = do
 
 presentationToContentTypes :: PandocMonad m => Presentation -> P m ContentTypes
 presentationToContentTypes p@(Presentation _ slides) = do
-  mediaInfos <- (mconcat . M.elems) <$> gets stMediaIds
+  mediaInfos <- mconcat . M.elems <$> gets stMediaIds
   filePaths <- patternsToFilePaths $ inheritedPatterns p
   let mediaFps = filter (match (compile "ppt/media/image*")) filePaths
   let defaults = [ DefaultContentType "xml" "application/xml"
diff --git a/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs b/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs
index c6d76424d..affec38aa 100644
--- a/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs
+++ b/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs
@@ -537,10 +537,10 @@ withAttr _ sp = sp
 blockToShape :: Block -> Pres Shape
 blockToShape (Plain ils) = blockToShape (Para ils)
 blockToShape (Para (il:_))  | Image attr ils (url, _) <- il =
-      (withAttr attr . Pic def (T.unpack url)) <$> inlinesToParElems ils
+      withAttr attr . Pic def (T.unpack url) <$> inlinesToParElems ils
 blockToShape (Para (il:_))  | Link _ (il':_) target <- il
                             , Image attr ils (url, _) <- il' =
-      (withAttr attr . Pic def{picPropLink = Just $ ExternalTarget target} (T.unpack url))
+      withAttr attr . Pic def{picPropLink = Just $ ExternalTarget target} (T.unpack url)
       <$> inlinesToParElems ils
 blockToShape (Table _ blkCapt specs thead tbody tfoot) = do
   let (caption, algn, _, hdrCells, rows) = toLegacyTable blkCapt specs thead tbody tfoot
@@ -721,7 +721,7 @@ makeNoteEntry (n, blks) =
   let enum = Str (tshow n <> ".")
   in
     case blks of
-      (Para ils : blks') -> (Para $ enum : Space : ils) : blks'
+      (Para ils : blks') -> Para (enum : Space : ils) : blks'
       _ -> Para [enum] : blks
 
 forceFontSize :: Pixels -> Pres a -> Pres a
@@ -767,7 +767,7 @@ getMetaSlide  = do
          mempty
 
 addSpeakerNotesToMetaSlide :: Slide -> [Block] -> Pres (Slide, [Block])
-addSpeakerNotesToMetaSlide (Slide sldId layout@(MetadataSlide{}) spkNotes) blks =
+addSpeakerNotesToMetaSlide (Slide sldId layout@MetadataSlide{} spkNotes) blks =
   do let (ntsBlks, blks') = span isNotesDiv blks
      spkNotes' <- mconcat <$> mapM blockToSpeakerNotes ntsBlks
      return (Slide sldId layout (spkNotes <> spkNotes'), blks')
diff --git a/src/Text/Pandoc/Writers/RTF.hs b/src/Text/Pandoc/Writers/RTF.hs
index 55c1b470b..e3966ed07 100644
--- a/src/Text/Pandoc/Writers/RTF.hs
+++ b/src/Text/Pandoc/Writers/RTF.hs
@@ -241,12 +241,12 @@ blockToRTF _ _ b@(RawBlock f str)
   | otherwise         = do
       report $ BlockNotRendered b
       return ""
-blockToRTF indent alignment (BulletList lst) = (spaceAtEnd . T.concat) <$>
+blockToRTF indent alignment (BulletList lst) = spaceAtEnd . T.concat <$>
   mapM (listItemToRTF alignment indent (bulletMarker indent)) lst
 blockToRTF indent alignment (OrderedList attribs lst) =
-  (spaceAtEnd . T.concat) <$>
+  spaceAtEnd . T.concat <$>
    zipWithM (listItemToRTF alignment indent) (orderedMarkers indent attribs) lst
-blockToRTF indent alignment (DefinitionList lst) = (spaceAtEnd . T.concat) <$>
+blockToRTF indent alignment (DefinitionList lst) = spaceAtEnd . T.concat <$>
   mapM (definitionListItemToRTF alignment indent) lst
 blockToRTF indent _ HorizontalRule = return $
   rtfPar indent 0 AlignCenter "\\emdash\\emdash\\emdash\\emdash\\emdash"
diff --git a/src/Text/Pandoc/Writers/TEI.hs b/src/Text/Pandoc/Writers/TEI.hs
index ddf1d76e3..a9ee5eece 100644
--- a/src/Text/Pandoc/Writers/TEI.hs
+++ b/src/Text/Pandoc/Writers/TEI.hs
@@ -205,14 +205,14 @@ tableRowToTEI :: PandocMonad m
               -> [[Block]]
               -> m (Doc Text)
 tableRowToTEI opts cols =
-  (inTagsIndented "row" . vcat) <$> mapM (tableItemToTEI opts) cols
+  inTagsIndented "row" . vcat <$> mapM (tableItemToTEI opts) cols
 
 tableHeadersToTEI :: PandocMonad m
                   => WriterOptions
                   -> [[Block]]
                   -> m (Doc Text)
 tableHeadersToTEI opts cols =
-  (inTags True "row" [("role","label")] . vcat) <$>
+  inTags True "row" [("role","label")] . vcat <$>
     mapM (tableItemToTEI opts) cols
 
 tableItemToTEI :: PandocMonad m
@@ -220,7 +220,7 @@ tableItemToTEI :: PandocMonad m
                -> [Block]
                -> m (Doc Text)
 tableItemToTEI opts item =
-  (inTags False "cell" [] . vcat) <$> mapM (blockToTEI opts) item
+  inTags False "cell" [] . vcat <$> mapM (blockToTEI opts) item
 
 -- | Convert a list of inline elements to TEI.
 inlinesToTEI :: PandocMonad m => WriterOptions -> [Inline] -> m (Doc Text)
diff --git a/src/Text/Pandoc/Writers/XWiki.hs b/src/Text/Pandoc/Writers/XWiki.hs
index cd72d9647..c35235650 100644
--- a/src/Text/Pandoc/Writers/XWiki.hs
+++ b/src/Text/Pandoc/Writers/XWiki.hs
@@ -45,7 +45,7 @@ import Text.Pandoc.Shared
 import Text.Pandoc.Writers.MediaWiki (highlightingLangs)
 import Text.Pandoc.Writers.Shared (toLegacyTable)
 
-data WriterState = WriterState {
+newtype WriterState = WriterState {
   listLevel :: Text -- String at the beginning of items
 }