OMath parser: Change signature of exported function.

This changes the signature of the exported `readOMML` to `String ->
Either String [Exp]`, so it can now, in theory, be slotted into
TeXMath. It doesn't have any real error reporting yet, but that might
make more sense once I put it in a branch, and understand how it works
in the other readers.

It also now reads strings that parse to either oMath or oMathPara
elements. Note that the distinction is lost in the output. It's up to
the caller to remember the display type.

2 files changed, 20 insertions, 7 deletions

diff --git a/src/Text/Pandoc/Readers/Docx/OMath.hs b/src/Text/Pandoc/Readers/Docx/OMath.hs
index 62fc6286c..47f8dd197 100644
--- a/src/Text/Pandoc/Readers/Docx/OMath.hs
+++ b/src/Text/Pandoc/Readers/Docx/OMath.hs
@@ -38,11 +38,20 @@ import Data.Maybe (mapMaybe, fromMaybe)
 import Data.List (intersperse)
 import qualified Text.TeXMath.Types as TM
 
-readOMML :: Element -> Maybe [TM.Exp]
-readOMML element  | isElem "m" "oMath" element =
+readOMML :: String -> Either String [TM.Exp]
+readOMML s | Just e <- parseXMLDoc s =
+  case elemToOMML e of
+    Just exs -> Right exs
+    Nothing   -> Left "xml file was not an <m:oMathPara> or <m:oMath> element."
+readOMML _ = Left "Couldn't parse OMML file"
+
+elemToOMML :: Element -> Maybe [TM.Exp]
+elemToOMML element  | isElem "m" "oMathPara" element = do
+  let expList = mapMaybe elemToOMML (elChildren element)
+  return $ map (\l -> if length l == 1 then (head l) else TM.EGrouped l) expList
+elemToOMML element  | isElem "m" "oMath" element =
   Just $ concat $ mapMaybe (elemToExps') (elChildren element)
-readOMML _ = Nothing
-
+elemToOMML _ = Nothing
 
 isElem :: String -> String -> Element -> Bool
 isElem prefix name element =
diff --git a/src/Text/Pandoc/Readers/Docx/Parse.hs b/src/Text/Pandoc/Readers/Docx/Parse.hs
index 8c9b4d672..beb58fed2 100644
--- a/src/Text/Pandoc/Readers/Docx/Parse.hs
+++ b/src/Text/Pandoc/Readers/Docx/Parse.hs
@@ -86,6 +86,10 @@ maybeToD :: Maybe a -> D a
 maybeToD (Just a) = return a
 maybeToD Nothing = throwError DocxError
 
+eitherToD :: Either a b -> D b
+eitherToD (Right b) = return b
+eitherToD (Left _)  = throwError DocxError
+
 concatMapM        :: (Monad m) => (a -> m [b]) -> [a] -> m [b]
 concatMapM f xs   =  liftM concat (mapM f xs)
 
@@ -150,7 +154,7 @@ defaultParagraphStyle = ParagraphStyle { pStyle = []
 data BodyPart = Paragraph ParagraphStyle [ParPart]
               | ListItem ParagraphStyle String String Level [ParPart]
               | Tbl String TblGrid TblLook [Row]
-              | OMathPara [[Exp]]
+              | OMathPara [Exp]
               deriving Show
 
 type TblGrid = [Integer]
@@ -475,7 +479,7 @@ elemToBodyPart ns element
   | isElem ns "w" "p" element
   , (c:_) <- findChildren (elemName ns "m" "oMathPara") element =
       do
-        expsLst <- mapD (\e -> (maybeToD $ readOMML e)) (elChildren c)
+        expsLst <- eitherToD $ readOMML $ showElement c
         return $ OMathPara expsLst
 elemToBodyPart ns element
   | isElem ns "w" "p" element
@@ -575,7 +579,7 @@ elemToParPart ns element
       Nothing     -> ExternalHyperLink "" runs
 elemToParPart ns element
   | isElem ns "m" "oMath" element =
-    (maybeToD $ readOMML element) >>= (return . PlainOMath)
+    (eitherToD $ readOMML $ showElement element) >>= (return . PlainOMath)
 elemToParPart _ _ = throwError WrongElem
 
 lookupFootnote :: String -> Notes -> Maybe Element