Various minor cleanups and refactoring (#6117)

* Use concatMap instead of reimplementing it

* Replace an unnecessary multi-way if with a regular if

* Use sortOn instead of sortBy and comparing

* Use guards instead of lots of indents for if and else

* Remove redundant do blocks

* Extract common functions from both branches of maybe

Whenever both the Nothing and the Just branch of maybe do the same
function, do that function on the result of maybe instead.

* Use fmap instead of reimplementing it from maybe

* Use negative forms instead of negating the positive forms

* Use mapMaybe instead of mapping and then using catMaybes

* Use zipWith instead of mapping over the result of zip

* Use unwords instead of reimplementing it

* Use <$ instead of <$> and const

* Replace case of Bool with if and else

* Use find instead of listToMaybe and filter

* Use zipWithM instead of mapM and zip

* Inline lambda wrappers into the real functions

* We get zipWithM from Text.Pandoc.Writers.Shared

* Use maybe instead of fromMaybe and fmap

I'm not sure how this one slipped past me.

* Increase a bit of indentation

4 files changed, 21 insertions, 23 deletions

diff --git a/src/Text/Pandoc/Writers/Markdown.hs b/src/Text/Pandoc/Writers/Markdown.hs
index 10ab3dfe1..87e41b766 100644
--- a/src/Text/Pandoc/Writers/Markdown.hs
+++ b/src/Text/Pandoc/Writers/Markdown.hs
@@ -25,7 +25,7 @@ import Data.Char (isAlphaNum)
 import Data.Default
 import Data.List (find, intersperse, sortBy, transpose)
 import qualified Data.Map as M
-import Data.Maybe (fromMaybe, catMaybes)
+import Data.Maybe (fromMaybe, mapMaybe)
 import Data.Ord (comparing)
 import qualified Data.Set as Set
 import Data.Text (Text)
@@ -121,7 +121,7 @@ mmdTitleBlock (Context hashmap) =
                  | null xs        -> empty
                  | otherwise      -> k' <> ":" <> space <>
                                       hcat (intersperse "; " $
-                                          catMaybes $ map fromVal xs)
+                                            mapMaybe fromVal xs)
                (k', SimpleVal x)
                       | isEmpty x -> empty
                       | otherwise -> k' <> ":" <> space <>
@@ -256,7 +256,7 @@ keyToMarkdown opts (label', (src, tit), attr) = do
 notesToMarkdown :: PandocMonad m => WriterOptions -> [[Block]] -> MD m (Doc Text)
 notesToMarkdown opts notes = do
   n <- gets stNoteNum
-  notes' <- mapM (\(num, note) -> noteToMarkdown opts num note) (zip [n..] notes)
+  notes' <- zipWithM (noteToMarkdown opts) [n..] notes
   modify $ \st -> st { stNoteNum = stNoteNum st + length notes }
   return $ vsep notes'
 
@@ -647,8 +647,7 @@ blockToMarkdown' opts (OrderedList (start,sty,delim) items) = do
                                then m <> T.replicate (3 - T.length m) " "
                                else m) markers
   contents <- inList $
-              mapM (\(item, num) -> orderedListItemToMarkdown opts item num) $
-              zip markers' items
+              zipWithM (orderedListItemToMarkdown opts) markers' items
   return $ (if isTightList items then vcat else vsep) contents <> blankline
 blockToMarkdown' opts (DefinitionList items) = do
   contents <- inList $ mapM (definitionListItemToMarkdown opts) items
@@ -680,11 +679,11 @@ pipeTable headless aligns rawHeaders rawRows = do
                     hcat (intersperse (literal "|") $
                           zipWith3 blockFor aligns widths (map chomp cs))
                     <> literal "|"
-  let toborder (a, w) = literal $ case a of
-                             AlignLeft    -> ":" <> T.replicate (w + 1) "-"
-                             AlignCenter  -> ":" <> T.replicate w "-" <> ":"
-                             AlignRight   -> T.replicate (w + 1) "-" <> ":"
-                             AlignDefault -> T.replicate (w + 2) "-"
+  let toborder a w = literal $ case a of
+                          AlignLeft    -> ":" <> T.replicate (w + 1) "-"
+                          AlignCenter  -> ":" <> T.replicate w "-" <> ":"
+                          AlignRight   -> T.replicate (w + 1) "-" <> ":"
+                          AlignDefault -> T.replicate (w + 2) "-"
   -- note:  pipe tables can't completely lack a
   -- header; for a headerless table, we need a header of empty cells.
   -- see jgm/pandoc#1996.
@@ -692,7 +691,7 @@ pipeTable headless aligns rawHeaders rawRows = do
                   then torow (replicate (length aligns) empty)
                   else torow rawHeaders
   let border = nowrap $ literal "|" <> hcat (intersperse (literal "|") $
-                        map toborder $ zip aligns widths) <> literal "|"
+                        zipWith toborder aligns widths) <> literal "|"
   let body   = vcat $ map torow rawRows
   return $ header $$ border $$ body
 
diff --git a/src/Text/Pandoc/Writers/Powerpoint/Output.hs b/src/Text/Pandoc/Writers/Powerpoint/Output.hs
index 344a5564a..856dbfcd0 100644
--- a/src/Text/Pandoc/Writers/Powerpoint/Output.hs
+++ b/src/Text/Pandoc/Writers/Powerpoint/Output.hs
@@ -249,7 +249,7 @@ presentationToArchiveP p@(Presentation docProps slides) = do
   filePaths <- patternsToFilePaths $ inheritedPatterns p
 
   -- make sure all required files are available:
-  let missingFiles = filter (\fp -> not (fp `elem` filePaths)) requiredFiles
+  let missingFiles = filter (`notElem` filePaths) requiredFiles
   unless (null missingFiles)
     (throwError $
       PandocSomeError $
@@ -1539,15 +1539,15 @@ slideToSlideRelEntry slide = do
   element <- slideToSlideRelElement slide
   elemToEntry ("ppt/slides/_rels/" <> idNumToFilePath idNum <> ".rels") element
 
-linkRelElement :: PandocMonad m => Int -> LinkTarget -> P m Element
-linkRelElement rIdNum (InternalTarget targetId) = do
+linkRelElement :: PandocMonad m => (Int, LinkTarget) -> P m Element
+linkRelElement (rIdNum, InternalTarget targetId) = do
   targetIdNum <- getSlideIdNum targetId
   return $
     mknode "Relationship" [ ("Id", "rId" <> show rIdNum)
                           , ("Type", "http://schemas.openxmlformats.org/officeDocument/2006/relationships/slide")
                           , ("Target", "slide" <> show targetIdNum <> ".xml")
                           ] ()
-linkRelElement rIdNum (ExternalTarget (url, _)) = do
+linkRelElement (rIdNum, ExternalTarget (url, _)) = do
   return $
     mknode "Relationship" [ ("Id", "rId" <> show rIdNum)
                           , ("Type", "http://schemas.openxmlformats.org/officeDocument/2006/relationships/hyperlink")
@@ -1556,7 +1556,7 @@ linkRelElement rIdNum (ExternalTarget (url, _)) = do
                           ] ()
 
 linkRelElements :: PandocMonad m => M.Map Int LinkTarget -> P m [Element]
-linkRelElements mp = mapM (\(n, lnk) -> linkRelElement n lnk) (M.toList mp)
+linkRelElements mp = mapM linkRelElement (M.toList mp)
 
 mediaRelElement :: MediaInfo -> Element
 mediaRelElement mInfo =
diff --git a/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs b/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs
index 75ce0dd4e..d36c92fa3 100644
--- a/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs
+++ b/src/Text/Pandoc/Writers/Powerpoint/Presentation.hs
@@ -712,8 +712,8 @@ blocksToSlide blks = do
   slideLevel <- asks envSlideLevel
   blocksToSlide' slideLevel blks' spkNotes
 
-makeNoteEntry :: Int -> [Block] -> [Block]
-makeNoteEntry n blks =
+makeNoteEntry :: (Int, [Block]) -> [Block]
+makeNoteEntry (n, blks) =
   let enum = Str (tshow n <> ".")
   in
     case blks of
@@ -742,7 +742,7 @@ makeEndNotesSlideBlocks = do
                        ls -> ls
              ident = Shared.uniqueIdent exts title anchorSet
              hdr = Header slideLevel (ident, [], []) title
-             blks = concatMap (\(n, bs) -> makeNoteEntry n bs) $
+             blks = concatMap makeNoteEntry $
                     M.toList noteIds
          in return $ hdr : blks
 
diff --git a/src/Text/Pandoc/Writers/XWiki.hs b/src/Text/Pandoc/Writers/XWiki.hs
index 7afe845c7..4f9494933 100644
--- a/src/Text/Pandoc/Writers/XWiki.hs
+++ b/src/Text/Pandoc/Writers/XWiki.hs
@@ -54,10 +54,9 @@ type XWikiReader m = ReaderT WriterState m
 
 -- | Convert Pandoc to XWiki.
 writeXWiki :: PandocMonad m => WriterOptions -> Pandoc -> m Text
-writeXWiki _ (Pandoc _ blocks) = do
+writeXWiki _ (Pandoc _ blocks) =
   let env = WriterState { listLevel = "" }
-  body <- runReaderT (blockListToXWiki blocks) env
-  return $ body
+  in runReaderT (blockListToXWiki blocks) env
 
 -- | Concatenates strings with line breaks between them.
 vcat :: [Text] -> Text
@@ -219,7 +218,7 @@ inlineToXWiki (Link (id', _, _) txt (src, _)) = do
 inlineToXWiki (Image _ alt (source, tit)) = do
   alt' <- inlineListToXWiki alt
   let
-    params = intercalate " " $ filter (not . Text.null) [
+    params = Text.unwords $ filter (not . Text.null) [
         if Text.null alt' then "" else "alt=\"" <> alt' <> "\"",
           if Text.null tit then "" else "title=\"" <> tit <> "\""
         ]