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{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE UndecidableInstances #-}
{- |
Module : Text.Pandoc.Lua.Marshaling.List
Copyright : © 2012-2021 John MacFarlane
© 2017-2021 Albert Krewinkel
License : GNU GPL, version 2 or above
Maintainer : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
Stability : alpha
Marshaling/unmarshaling instances for @pandoc.List@s.
-}
module Text.Pandoc.Lua.Marshaling.List
( List (..)
) where
import Data.Data (Data)
import Foreign.Lua (Peekable, Pushable)
import Text.Pandoc.Walk (Walkable (..))
import Text.Pandoc.Lua.Util (defineHowTo, pushViaConstructor)
import qualified Foreign.Lua as Lua
-- | List wrapper which is marshalled as @pandoc.List@.
newtype List a = List { fromList :: [a] }
deriving (Data, Eq, Show)
instance Pushable a => Pushable (List a) where
push (List xs) =
pushViaConstructor "List" xs
instance Peekable a => Peekable (List a) where
peek idx = defineHowTo "get List" $ do
xs <- Lua.peek idx
return $ List xs
-- List is just a wrapper, so we can reuse the walk instance for
-- unwrapped Hasekll lists.
instance Walkable [a] b => Walkable (List a) b where
walkM f = walkM (fmap fromList . f . List)
query f = query (f . List)
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