More basic modules for errors and parsers

1 files changed, 20 insertions, 0 deletions

diff --git a/src/Prolog.hs b/src/Prolog.hs
index 70545c9..a688063 100644
--- a/src/Prolog.hs
+++ b/src/Prolog.hs
@@ -36,18 +36,22 @@ module Prolog
     , toSL
     , convS
     , convSL
+    , renderTo
+    , fromStringlike
     -- * Utils
     , (<<$>>)
     , (<<<$>>>)
     , (<<&>>)
     , (-->)
     , (-/>)
+    , (>>=?)
     , foreach
     , liftMaybe
     , squashMaybe
     ) where
 
 import Control.Applicative
+import Control.Comonad
 import Control.Monad
 import Control.Monad.Catch
 import Control.Monad.Except
@@ -110,6 +114,12 @@ infixr 0 -/>
 (-/>) = (-->) . fmap not
 {-# INLINE (-/>) #-}
 
+(>>=?) :: (Monad m, Monoid w) => m (Maybe a) -> (a -> m w) -> m w
+infixl 1 >>=?
+x >>=? f = x >>= maybe (pure mempty) f
+{-# INLINE (>>=?) #-}
+
+
 liftMaybe :: Alternative m => Maybe a -> m a
 liftMaybe = maybe empty pure
 {-# INLINE liftMaybe #-}
@@ -118,6 +128,13 @@ squashMaybe :: Alternative m => m (Maybe a) -> m a
 squashmaybe = (>>= liftMaybe)
 {-# INLINE squashMaybe #-}
 
+renderTo :: (StringConv T.Text s, L.Render r) => r -> s
+renderTo = toSL . L.render
+{-# INLINE renderTo #-}
+
+fromStringlike :: (IsString s, StringConv t String) => t -> s
+fromStringlike = fromString . toSL
+{-# INLINE fromStringlike #-}
 
 -- Orphan instances
 
@@ -134,6 +151,9 @@ instance H.Writable L.LaTeX where
 instance Contravariant H.Context where
     contramap f (H.Context c) = H.Context $ \x xs -> c x xs . fmap f
 
+instance Comonad H.Item where
+    extract = H.itemBody
+    duplicate = join (<$)
 
 instance StringConv L.LaTeX T.Text where
     strConv _ = L.render