Provide shared F monad functions for Markdown and Org readers

The `F` monads used for delayed evaluation of certain values in the
Markdown and Org readers are based on a shared data type capturing the
common pattern of both `F` types.

1 files changed, 9 insertions, 37 deletions

diff --git a/src/Text/Pandoc/Readers/Org/ParserState.hs b/src/Text/Pandoc/Readers/Org/ParserState.hs
index 6bed2a547..bdd1dc951 100644
--- a/src/Text/Pandoc/Readers/Org/ParserState.hs
+++ b/src/Text/Pandoc/Readers/Org/ParserState.hs
@@ -39,7 +39,7 @@ module Text.Pandoc.Readers.Org.ParserState
   , TodoState (..)
   , activeTodoMarkers
   , registerTodoSequence
-  , F(..)
+  , F
   , askF
   , asksF
   , trimInlinesF
@@ -50,14 +50,13 @@ module Text.Pandoc.Readers.Org.ParserState
   , optionsToParserState
   ) where
 
-import Control.Monad (liftM, liftM2)
-import Control.Monad.Reader (Reader, ReaderT, ask, asks, local, runReader)
+import Control.Monad.Reader (ReaderT, asks, local)
 
 import Data.Default (Default (..))
 import qualified Data.Map as M
 import qualified Data.Set as Set
 
-import Text.Pandoc.Builder (Blocks, Inlines, trimInlines)
+import Text.Pandoc.Builder (Blocks, Inlines)
 import Text.Pandoc.Definition (Meta (..), nullMeta)
 import Text.Pandoc.Options (ReaderOptions (..))
 import Text.Pandoc.Logging
@@ -65,7 +64,12 @@ import Text.Pandoc.Parsing (HasHeaderMap (..), HasIdentifierList (..),
                             HasLogMessages (..),
                             HasLastStrPosition (..), HasQuoteContext (..),
                             HasReaderOptions (..), ParserContext (..),
-                            QuoteContext (..), SourcePos)
+                            QuoteContext (..), SourcePos, Future,
+                            askF, asksF, returnF, runF, trimInlinesF)
+
+-- | This is used to delay evaluation until all relevant information has been
+-- parsed and made available in the parser state.
+type F = Future OrgParserState
 
 -- | An inline note / footnote containing the note key and its (inline) value.
 type OrgNoteRecord = (String, F Blocks)
@@ -229,35 +233,3 @@ defaultExportSettings = ExportSettings
   , exportWithEmail = True
   , exportWithTodoKeywords = True
   }
-
-
---
--- Parser state reader
---
-
--- | Reader monad wrapping the parser state.  This is used to delay evaluation
--- until all relevant information has been parsed and made available in the
--- parser state.  See also the newtype of the same name in
--- Text.Pandoc.Parsing.
-newtype F a = F { unF :: Reader OrgParserState a
-                } deriving (Functor, Applicative, Monad)
-
-instance Monoid a => Monoid (F a) where
-  mempty = return mempty
-  mappend = liftM2 mappend
-  mconcat = fmap mconcat . sequence
-
-runF :: F a -> OrgParserState -> a
-runF = runReader . unF
-
-askF :: F OrgParserState
-askF = F ask
-
-asksF :: (OrgParserState -> a) -> F a
-asksF f = F $ asks f
-
-trimInlinesF :: F Inlines -> F Inlines
-trimInlinesF = liftM trimInlines
-
-returnF :: Monad m => a -> m (F a)
-returnF = return . return