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Compat stuff for Monoid / Semigroup

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Tissevert 2019-05-16 21:40:19 +02:00
parent 96190a8ca4
commit 088637b2c0
1 changed files with 15 additions and 1 deletions
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16
src/PDF/Output.hs
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@ -1,3 +1,4 @@
{-# LANGUAGE CPP #-}
module PDF.Output ( module PDF.Output (
OBuilder(..) OBuilder(..)
, Output(..) , Output(..)
@ -13,6 +14,9 @@ module PDF.Output (
import Data.ByteString.Builder (Builder, char8, lazyByteString, string8, toLazyByteString) import Data.ByteString.Builder (Builder, char8, lazyByteString, string8, toLazyByteString)
import Data.ByteString.Lazy.Char8 (ByteString) import Data.ByteString.Lazy.Char8 (ByteString)
-- #if MIN_VERSION_base(4,9,0)
-- import qualified Data.Semigroup as Sem
-- #endif
import Data.String (IsString(..)) import Data.String (IsString(..))
import Control.Monad.Reader (MonadReader(..), Reader, runReader) import Control.Monad.Reader (MonadReader(..), Reader, runReader)
import qualified PDF.EOL as EOL (Style(..)) import qualified PDF.EOL as EOL (Style(..))
@ -22,9 +26,19 @@ newtype OBuilder = OBuilder (Reader EOL.Style Builder)
lift :: (a -> Builder) -> a -> OBuilder lift :: (a -> Builder) -> a -> OBuilder
lift f a = OBuilder $ return (f a) lift f a = OBuilder $ return (f a)
append :: OBuilder -> OBuilder -> OBuilder
append (OBuilder a) (OBuilder b) = OBuilder (mappend <$> a <*> b)
#if MIN_VERSION_base(4,9,0)
instance Semigroup OBuilder where
(<>) = append
#endif
instance Monoid OBuilder where instance Monoid OBuilder where
mempty = OBuilder (return mempty) mempty = OBuilder (return mempty)
mappend (OBuilder a) (OBuilder b) = OBuilder (mappend <$> a <*> b) #if !(MIN_VERSION_base(4,9,0))
mappend = append
#endif
instance IsString OBuilder where instance IsString OBuilder where
fromString = string fromString = string